United States

Environmental Protection

Agency

Building Decontamination Alternatives

Offi ce of Research and Development

National Homeland Security 

Research Center

COMPILATION OF AVAILABLE DATA ON
September 2006

Errata Sheet

Compilation of Available Data on Building

Decontamination Alternatives

Publication # EPA 600/R‐05/036, March 2005

Document page 65 (pdf page 78), Section 3.4 References

For the reference:

Tyerech, 1998. Tyerech, Michael Richard.  Shelf stable hydrogen peroxide containing

carpet cleaning and treatment compositions. U. S. Patent No. 5,728,669. March 17,

1998.

Change to read:

Tyerech, 1998. Tyerech, Michael Richard.  Shelf stable hydrogen peroxide containing

carpet cleaning and treatment compositions. U. S. Patent No. 5,728,660. March 17,

1998.

[The Patent No. has been corrected from U. S. Patent No. 5,728,669 to U. S. Patent No.

5,728,660.]
EPA/600/R-05/036

March 2005

COMPILATION OF AVAILABLE DATA ON

BUILDING DECONTAMINATION ALTERNATIVES

Prepared by

Science Applications International Corporation

11251 Roger Bacon Drive

Reston, VA 20190

EPA Contract No. 68-C-02-067

EPA Work Assignment (WA) 1-31

Prepared for

U.S. Environmental Protection Agency

National Homeland Security Research Center

Office of Research and Development

Washington, D.C. 20460
ii

EPA DISCLAIMER NOTICE

This report was prepared in an effort to promptly provide as much information as

possible on technologies that could potentially be utilized in decontamination of a building that

has been subjected to a chemical or biological attack. As a result, this report has compiled large

amounts of data from a variety of sources, often including the vendors of the technologies being

addressed. It has not been possible to independently evaluate the data that are presented. 

Accordingly, the appearance of data in this report should not be interpreted as implying EPA

validation of these data, or of the experimental protocols or quality assurance measures used in

generating the data.

Mention of trade names or commercial products does not constitute endorsement or

recommendation of their use.
iii

ABSTRACT

In September 2002, the U.S. Environmental Protection Agency (EPA) created the National

Homeland Security Research Center (NHSRC) within the Agency’s Office of Research and

Development (ORD). As one of the elements within NHSRC, the Safe Buildings Team has, as a

key part of its responsibilities, engineering and economic analysis of alternative technologies and

approaches for decontaminating buildings following an attack using chemical and biological

(CB) agents.

As an initial step in this Safe Buildings Team decontamination program, NHSRC commissioned

this state-of-the-art report, to provide background information regarding potential building

decontamination technologies. This review of decontamination technologies is intended to: 1)

assist NHSRC in prioritizing the technologies to be evaluated under its decontamination

program; and 2) serve as an educational tool for the various NHSRC clients interested in

building decontamination.

This document presents an analysis of selected technologies that have been tested for their

potential effectiveness in decontaminating a building that has been attacked using biological or

chemical warfare agents, or using toxic industrial compounds. The technologies selected to be

addressed here fall into three broad categories:

 • Liquid-based topical agents, including hypochlorite (bleach), aqueous chlorine dioxide,

aqueous hydrogen peroxide, and a proprietary product (TechXtract).

 • Foams and gels, including Sandia Foam and Decon Green, CASCAD, and L-Gel.

 • Gaseous and vapor technologies (fumigants), including chlorine dioxide gas, vapor-phase

hydrogen peroxide, paraformaldehyde, and methyl bromide.

Each of these technologies is reviewed in terms of its principles of operation, technical maturity,

available data, concerns for the user, commercial availability, and advantages and disadvantages. 

No single technology is applicable in all situations; some technologies are better selections than

others. As a broad generality, liquids are effective cleaners of non-porous surfaces, but may

cause corrosion or degradation of the surface. Foams and gels have shown some promising

results against both biological and chemical contaminants, but present post-decontamination

cleanup issues, and require further demonstration. Gases and vapors have been demonstrated to

be effective in destroying biological contamination under controlled conditions (e.g., in

sterilization chambers) and, in some cases, in field remediations, but have not been effective in

removing chemical contamination, and warrant further demonstration under the less well

controlled conditions that exist during fumigation of a large building.

This document has been peer and administratively reviewed by the U.S. Environmental

Protection Agency, and approved for publication. Mention of trade names or commercial

products does not constitute endorsement or recommendation of their use.
iv

TABLE OF CONTENTS

EPA Disclaimer Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

1. EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Decontamination Technologies Addressed in this Document ................1

1.3 Summary of Technology Status ......................................2

1.4 Identification of Areas for Potential Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.5 The NHSRC Program to Address these Research Areas . . . . . . . . . . . . . . . . . . . 11

2. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.1 Scope, Purpose, and Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 Summary of Decontamination Technologies Selected for Evaluation . . . . . . . . 13

2.2.1 Surface-Applied Technologies Considered . . . . . . . . . . . . . . . . . . . . . . . 14

2.2.2 Gas- and Vapor-Phase Technologies Considered . . . . . . . . . . . . . . . . . . 17

2.2.3 Other Technologies Considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.3 Broad Review of Categories of Alternatives with Potential Applications . . . . . 20

2.4 References for Section 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3. LIQUID-BASED TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1 Hypochlorite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1.1 Technology Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.1.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.1.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.1.5 Concerns for the User (Applicability) . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.1.6 Availability of the Technology for Commercial Applications . . . . . . . . 30

3.1.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.1.8 Potential Areas for Future Research (Uncertainties) . . . . . . . . . . . . . . . . 31

3.1.9 References for Section 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.2 Aqueous Chlorine Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.2.1 Technology Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.2.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.2.3 Applications of Aqueous Chlorine Dioxide . . . . . . . . . . . . . . . . . . . . . . . 32

3.2.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.2.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.2.6 Availability of the Technology for Commercial Applications . . . . . . . . 40

3.2.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.2.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.2.9 References for Section 3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
v

3.3 Liquid Hydrogen Peroxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.3.1 Technology Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.3.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.3.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.3.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.3.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3.3.6 Availability of the Technology for Commercial Applications . . . . . . . . 52

3.3.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3.3.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

3.3.9 References for Section 3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

3.4 TechXtract® Contaminant Extraction Technology . . . . . . . . . . . . . . . . . . . . . . . 55

3.4.1 Description of the Technology Alternative . . . . . . . . . . . . . . . . . . . . . . . 55

3.4.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

3.4.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

3.4.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

3.4.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

3.4.6 Availability of the technology for commercial applications . . . . . . . . . . 63

3.4.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

3.4.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

3.4.9 References for Section 3.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4. FOAM AND GEL TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.1 Sandia Foam and Decon Green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.1.1 Technology Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.1.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4.1.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4.1.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

4.1.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.1.6 Availability of the Technology for Commercial Applications . . . . . . . . 75

4.1.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.1.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.1.9 References for Section 4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.2 Canadian Aqueous System for Chemical-Biological Agent Decontamination

(CASCAD®) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

4.2.1 Technology Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

4.2.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4.2.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4.2.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4.2.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.2.6 Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.2.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.2.8 Potential areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.2.9 References for Section 4.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
vi

4.3 L-Gel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.3.1 Description of the Technology Alternative . . . . . . . . . . . . . . . . . . . . . . . 87

4.3.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

4.3.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.3.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.3.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

4.3.6 Availability of the Technology for Commercial Applications . . . . . . . . 93

4.3.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

4.3.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

4.3.9 References for Section 4.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

5. GAS AND VAPOR TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

5.1 Chlorine Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

5.1.1 Description of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

5.1.2 Methods for the Generation of Chlorine Dioxide . . . . . . . . . . . . . . . . . . 98

5.1.3 Applications for Chlorine Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

5.1.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.1.4.1 Data from laboratory and trailer testing . . . . . . . . . . . . . . . . . . . 101

5.1.4.2 Experience with field fumigation of buildings . . . . . . . . . . . . . 116

5.1.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

5.1.6 Availability of the Technology for Commercial Applications . . . . . . . 126

5.1.7 Cost for generation of ClO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.1.8 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.1.9 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.1.10 References for Section 5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.2 Vapor Hydrogen Peroxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

5.2.1 Description of the Technology Alternative . . . . . . . . . . . . . . . . . . . . . . 136

5.2.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

5.2.3 Applications for Hydrogen Peroxide Vapor . . . . . . . . . . . . . . . . . . . . . 138

5.2.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.4.1 Data from laboratory testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.4.2 Experience with field fumigation of buildings . . . . . . . . . . . . . 143

5.2.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

5.2.6 Availability of the Technology for Commercial Applications . . . . . . . 148

5.2.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

5.2.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

5.2.9 References for Section 5.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

5.3 Paraformaldehyde . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

5.3.1 Description of the Technology Alternative . . . . . . . . . . . . . . . . . . . . . . 151

5.3.2 Technical Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

5.3.3 Applications of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

5.3.4 Compilation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

5.3.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

5.3.6 Availability of the Technology for Commercial Applications . . . . . . . 164

5.3.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

5.3.8 Potential Areas for Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
vii

5.3.9 References for Section 5.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

5.4 Methyl Bromide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

5.4.1 Description of the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

5.4.2 Technical maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

5.4.3 Applications of the technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

5.4.4 Compilation of available data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

5.4.5 Concerns for the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

5.4.6 Availability of the technology for commercial applications . . . . . . . . . 179

5.4.7 Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

5.4.8 Potential areas for future research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

5.4.9 References for Section 5.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
viii

LIST OF FIGURES

Figure 3.4-1. Locations of Wipe and Coring Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Figure 4.1-1. EPA Test Data for EasyDECON 4215 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Figure 4.2-1. Demonstration of the Foam Application on a Tank Vehicle . . . . . . . . . . . . . . . . 81

Figure 4.3-1. L-Gel, Delivered as Semisolid, is Liquified for Use . . . . . . . . . . . . . . . . . . . . . . 88

Figure 5.1-1. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 11;

Laboratory Validation of Chlorine Dioxide Decontamination . . . . . . . . . . . . . . . . . . . 104

Figure 5.1-2. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 9;

Laboratory Validation of Chlorine Dioxide Decontamination . . . . . . . . . . . . . . . . . . . 105

Figure 5.1-3. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 5;

Laboratory Validation of Chlorine Dioxide Decontamination . . . . . . . . . . . . . . . . . . . 106

Figure 5.1-4. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 1;

Laboratory Validation of Chlorine Dioxide Decontamination . . . . . . . . . . . . . . . . . . . 106

Figure 5.1-5. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 10;

Laboratory Validation of Chlorine Dioxide Decontamination . . . . . . . . . . . . . . . . . . . 107

Figure 5.1-6. Chlorine Dioxide Generation System and Interior Operations . . . . . . . . . . . . . . 109

Figure 5.1-7. Beltsville Data for Bacillus subtilis spore strip analysis at various conditions . 111

Figure 5.1-8. Beltsville Data for Bacillus stearothermophilus spore strip analysis . . . . . . . . . 112

Figure 5.1-9. Bleaching Effect on Photographic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Figure 5.2-1. Chemical Reactions to Generate and Remove Hydrogen Peroxide from the Air 136

Figure 5.2-2. The Clarus C and Claris L Units for Hydrogen Peroxide Vapor Generation . . 137

Figure 5.2-3. The Steris VHP 1000 Hydrogen peroxide vapor System . . . . . . . . . . . . . . . . . 137

Figure 5.2-4. Hydrogen Peroxide Vapor Concentration versus D-Value . . . . . . . . . . . . . . . . . 140

Figure 5.2-5. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial 6;

Laboratory Validation of Hydrogen Peroxide Decontamination . . . . . . . . . . . . . . . . . . 143

Figure 5.3-1. Percent Survival of Test Organisms after Decontamination with Various

Concentrations of Formaldehyde . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Figure 5.3-2. Percent Survival of Test Organisms after Decontamination at Various Relative

Humidities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

Figure 5.3-3. Percent Survival of Test Organisms with Variation of Temperature During

Decontamination with Paraformaldehyde at 10.5 G/m3

 and a Relative Humidity of

Approximately 58 Percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

Figure 5.4-1. Abstract of Scheffrahn and Weinberg Study . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Figure 5.4-2. Trailer configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Figure 5.4-3. Spore strip sites 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Figure 5.4-4. Spore strip site 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Figure 5.4-5. Spore strip site 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

Figure 5.4-6. The Prepared Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

Figure 5.4-7. Methyl Bromide Concentration During Trailer Fumigation and Aeration . . . . . 175

Figure 5.4-8. Summary of IITRI Research Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
ix

LIST OF TABLES

Table 1.3-1. Summary Table of Applicable Technologies ..............................4

Table 1.3-2. Summary of Technology Application Issues ..............................8

Table 1.4-1. Potential Research Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 3.1-1. Hypochlorite Decontaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 3.1-2. Residual Agent after Decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 3.2-1. Deactivation of Listeria monocytogenes Using Chlorine Dioxide Solutions . . . . 34

Table 3.2-2. Effect of Adding Acid to Stabilized Chlorine Dioxide Solution . . . . . . . . . . . . . . 34

Table 3.2-3. Effectiveness of Acidified Stabilized Chlorine Dioxide on Bacteria . . . . . . . . . . . 35

Table 3.2-4. Coliform Reduction in Drinking Water Treated with Chlorine Dioxide . . . . . . . . 35

Table 3.2-5. Chlorine Dioxide Concentration for 5-log Reduction in 

Cell Count at 60 Seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 3.2-6. Inactivation of Bacteria with Chlorine Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 3.2-7. Mortality of Fungi After in vitro Contact with ClO2 at 

Various Concentrations and Contact Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table 3.2-8. ClO2 Control of Poliovirus I. in Treated Sewage . . . . . . . . . . . . . . . . . . . . . . . . . 39

Table 3.2-9. ClO2 Bio-Fouling Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Table 3.3-1. Reaction of Hydrogen Peroxide-Containing Solutions with Chemical Agents . . . 46

Table 3.3-2. Effect of pH on VX Detoxification Using Hydrogen Peroxide . . . . . . . . . . . . . . . 47

Table 3.3-3. Effectiveness of Hydrogen Peroxide and Catalysts on Chemical Agents . . . . . . . 48

Table 3.3-4. Reduction of Bacteria in Sponges Following Hydrogen Peroxide Treatment . . . . 49

Table 3.3-5. Performance of Hydrogen Peroxide-Containing Formulation 

Sprayed Onto Glass Slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table 3.3-6. Effectiveness of Hydrogen Peroxide on Biological Agents . . . . . . . . . . . . . . . . . . 51

Table 3.4-1. Surface PCB Removal Based on Wipe Samples . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Table 3.4-2. PCB Removal at Depth Based on Corings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Table 3.4-3. Gas Turbine Generator PCDD/PCDF Wipe Samples Before and After . . . . . . . . 62

Table 4.1-1. Summary Reaction Rates of Agent Simulant Testing . . . . . . . . . . . . . . . . . . . . . . 70

Table 4.1-2. Live agent kill rate summary (testing conducted at IIT Research Institute) . . . . . 70

Table 4.1-3. B. globigii (Anthrax Simulant) Spore Kill During Dugway Filed Tests . . . . . . . . 71

Table 4.1-4. Percent Decontamination in Live Agent Testes at ECBC . . . . . . . . . . . . . . . . . . . 71

Table 4.1-5. Modec Decon Foam against Toxic Industrial Chemicals . . . . . . . . . . . . . . . . . . . 72

Table 4.1-6. Decontamination of CARC Panelsa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Table 4.2-1. Comparison of CASCAD to DS2 and C8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Table 4.2-2. CASCAD Effectiveness Against Chemical Warfare Agents . . . . . . . . . . . . . . . . 83

Table 4.2-3. Effectiveness of CASCAD Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Table 4.3-1. Surrogate Spore Counts Before and After L-Gel Treatment . . . . . . . . . . . . . . . . . 92

Table 5.1-1. Effect of ClO2 Gas Concentration on the Rate of Inactivation of 106

B. subtilis Spores on Paper Strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Table 5.1-2. Vendors for ClO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Table 5.2-1. Effectiveness of Liquid and Hydrogen Peroxide Vapor on Spores . . . . . . . . . . . 139

Table 5.2.2. D-Values of Bacterial Spores Exposed to Hydrogen Peroxide Vapor . . . . . . . . . 140

(continued)
x

LIST OF TABLES (concluded)

Table 5.2-3. Hydrogen Peroxide Vapor Efficacy at Various Temperatures 

against Geobacillus stearothermophilus spores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Table 5.3-1. Survival of Test Organisms on Strips Positioned at Different 

Test Locations During Decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

Table 5.3-2. The Effects of Formaldehyde on Various Organisms . . . . . . . . . . . . . . . . . . . . . 157

Table 5.3-3. Measured Average Conditions and Experimental Kill of B. Globigii . . . . . . . . . 158

Table 5.3-4. Paraformaldehyde Sterilization of Facilities, Materials, and Equipment . . . . . . . 159

Table 5.3-5. Percent Recovery of B. subtilis in Test Tubes with Paper Closures . . . . . . . . . . 160

Table 5.3-6. Percent Recovery of B. subtilis in Test Tubes with Glassine Closures . . . . . . . . 161

Table 5.3-7. Percent Recovery of B. subtilis in Test Tubes with Cotton Plug Closures . . . . . 161

Table 5.4-1. Global Methyl Bromide Pre-Plant Soil Fumigation: Usage of 

Methyl Bromide for Pre-plant soil Applications by Country (1996) . . . . . . . . . . . . . . . 169

Table 5.4-2. Spore Germination After Methyl Bromide Exposure . . . . . . . . . . . . . . . . . . . . . 170

Table 5.4-3. Germination of Spores After Exposure to Methyl Bromide, Second Test . . . . . . 171

Table 5.4-4. Spore Strip Location, Proximal Ambient Temperature Conditions, and 

Incubation Results for 80 Strips After Exposure for 48 Hours to Methyl Bromide 

at a Concentration of 303.7 oz/1,000ft3

 in Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
xi

ACKNOWLEDGMENTS

This report was initially compiled by R. Paul Schaudies, John B. Vierow, William Ellis,

Fred Myers, and Mary L. Wolfe from Science Applications International Corp. (SAIC) of

McLean, VA, through Work Assignment 1-31 issued under EPA Contract No. 68-C-02-067. 

Sections describing the decontamination of Federal buildings following the 2001 anthrax mail

incident were prepared by D. Bruce Henschel, the former lead for the building decontamination

program within the National Homeland Security Research Center of EPA’s Office of Research

and Development (ORD). Mr. Henschel also provided substantial additional technical input and

technical editing in the finalization of this document, and served as a technical consultant during

SAIC’s conduct of the Work Assignment. Scott R. Hedges of the National Risk Management

Research Laboratory (NRMRL) in ORD served as the Work Assignment Manager.

Special recognition is given to several individuals within EPA who provided detailed

technical reviews of the draft document, based upon their direct experience with the building

remediation activities that followed the October 2001 anthrax mail incident. These individuals

include: Carlton (Jeff) Kempter, in the Antimicrobials Division of EPA’s Office of Pesticide

Programs; Dorothy A. Canter, in the Office of the Assistant Administrator for EPA’s Office of

Solid Waste and Emergency Response; and G. Blair Martin, Associate Director of NRMRL’s

Air Pollution Prevention and Control Division.
xii

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1

1. EXECUTIVE SUMMARY

1.1 Objective

In September 2002, the U.S. Environmental Protection Agency (EPA) created the National

Homeland Security Research Center (NHSRC) within the Agency’s Office of Research and

Development (ORD). As one of the elements within NHSRC, the Safe Buildings Team has, as a

key part of its responsibilities, engineering and economic analysis of alternative technologies and

approaches for decontaminating buildings following an attack using chemical and biological

(CB) agents. The ultimate objective of this decontamination program is to produce a rigorous

guidance document that can assist a range of users – including governmental agencies, building

owners and operators, and cleanup contractors – in most effectively selecting and implementing

the decontamination approach for any particular building following a CB attack.

As an initial step in this Safe Buildings decontamination program, NHSRC commissioned this

report, to provide background information regarding potential building decontamination

technologies. This state-of-the-art review of decontamination technologies is intended to: 1)

assist NHSRC in prioritizing the technologies to be evaluated under its decontamination

program; and 2) serve as an educational tool for the various NHSRC clients interested in

building decontamination.

1.2 Decontamination Technologies Addressed in this Document

This document presents an analysis of technologies that have been tested for their potential

effectiveness in decontaminating a building that has been attacked using biological or chemical

warfare agents, or using toxic industrial compounds. This document does not present an

exhaustive evaluation of all potential technologies. Rather, the focus is on what are currently 

felt to be the most promising technologies, based upon commercial use in related applications

(e.g., medical sterilization), and based upon their apparent potential for possible use in building

decontamination. The technologies presented in this document include:

C Hypochlorite

C Aqueous chlorine dioxide

C Aqueous hydrogen peroxide

C TechXtract®

C Sandia Foam and Decon Green

C CASCAD®

C L-Gel

C Chlorine dioxide gas

C Hydrogen peroxide vapor

C Paraformaldehyde

C Methyl bromide
2

Before a chemical product intended for use in decontaminating biological agents may be sold or

distributed in the United States, EPA must either register that product as a pesticide under the

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), or, in the absence of registration,

must grant a crisis exemption allowing its use. Once registered or exempted for this use, the

pesticide would be commercially and legally available for use in accordance with the terms of

the registration or exemption. To date, EPA has not issued any registrations for decontamination

of biological threat agents in buildings, but has issued crisis exemptions that have permitted the

unregistered use of a number of liquid and gaseous and vapor products for the treatment of

Bacillus anthracis. EPA performed a full review of available data for each product along with

the remediation action plans for each site to ensure the product would be used safely and would

likely be effective against Bacillus anthracis. A list of the crisis exemptions approved to date by

EPA is found at www.epatechbit.org under "Crisis Exemptions."

 

There are additional technologies that are in the pipeline that could be effective for building

remediation efforts. Because they are still under evaluation, these technologies are not addressed

in this report. In addition, standard chemical spill technologies, such as the use of absorbents,

can be considered as well. Prior to selecting the agent(s) judged to be most appropriate for

remediating a contaminated building, the user should consider the type and layout of the

contaminated building; the materials in the building; the nature and extent of the contamination;

the toxicity, penetrability, and materials compatibility of the potential agent(s); the aeration of

the agent and any other by-products produced during the clean-up; history of usage of the

agent(s); the time required to complete the remediation; and the cost of the overall process.

1.3 Summary of Technology Status

The technologies evaluated fall into three broad categories – liquids, foams andgels, and gases

and vapors. Each has advantages and disadvantages depending upon the type of contaminant,

the type of materials to be decontaminated, and the size of the remediation area. No single

technology is applicable in all situations; some technologies are better selections than others. As

a broad generality, liquids are effective cleaners of non-porous surfaces, but may cause corrosion

or degradation of the surface. Foams and gels have shown some promising results against both

biological and chemical contaminants, but present post-decontamination cleanup issues, and

require further demonstration. Gases and vapors have been demonstrated to be effective in

destroying biological contamination under controlled conditions (e.g., in sterilization chambers),

but have not been effective in removing chemical contamination. There have been several

demonstrations of gaseous fumigants for the biological decontamination of portions (or the

entirety) of buildings under the less well controlled conditions that exist in the field, but further

field tests are required to demonstrate the practical engineering and economic applicability of

some of the fumigants.

Table 1.3-1 presents a summary of the technologies evaluated in this report, their technical

maturity (i.e., whether under development, demonstrated but not available, commercially

available, and whether approved by EPA for use as a pesticide), the type(s) of contaminant to

which they are applicable, the types of building applications in which they can be used, and a

summary of their effectiveness. Within the context of this report, “commercially available”

indicates that the technology is available for purchase; however, as discussed above, if the
3

technology is to be used to against biological agents, the technology would require EPA

approval for use as a pesticide. 

Table 1.3-2 summarizes treatment issues to consider in selecting a technology, including

compatibility of the technology with typical building materials, a summary of the types of

residuals that will be generated from treatment, and information on performance of or need for

specialized hardware.

More detailed information on each technology can be found in Sections 3 through 5 of this

report.
4

Table 1.3-1. Summary Table of Applicable Technologies

Technology Technical

Maturity

Applicable Agents Scope of Building

Applications

Effectiveness 

Hypochlorite Mature,

commercially

available.

Chemical agents:

(nerve and blister)

Biological agents

(Bacillus

anthracis) 

Treatment of

contaminated

surfaces in sites of

varying sizes.

Reports state the

effectiveness on chemical

agents, but no data are

available. A 6 log kill of

Bacillus subtilis was

achieved on hard, nonporous surface treated

with sodium hypochlorite

at pH 7 with a 60-minute

contact time. 

Aqueous chlorine

dioxide

Mature,

commercially

available.

Biological agents Treatment of

contaminated

surfaces in sites of

varying sizes.

EPA has data showing the

efficacy of 500 ppm

aqueous chlorine dioxide

on hard, non-porous

surfaces after 30 minute

contact time. EPA issued

a crisis exemption for

building surfaces on this

basis.

Aqueous

hydrogen

peroxide

Mature,

commercially

available.

Chemical agents:

(nerve and blister)

Biological agents

Treatment of

contaminated

surfaces in sites of

varying sizes.

EPA reviewed data from

companies showing the

efficacy of one hydrogen

peroxide product and four

hydrogen peroxide &

peracetic acid mixture

products with contact

times ranging from 10 to

30 minutes. On the basis

of these data, EPA issued

crisis exemptions for the

use of these products on 

building surfaces.

TechXtract Innovative,

commercially

available.

Toxic industrial

materials

Removal of organics

from porous materials

(e.g., concrete floors)

and from metal

equipment.

Greater than 99.93%

reduction in dioxin/furan

concentrations; variable

performance on removal

of PCBs from concrete.

Sandia Foam and

Decon Green

Sandia Foam:

Commerciallyavailable, full

scale

Decon Green:

Not

commercially

available

Chemical agents:

(nerve and blister)

Biological agents

(Bacillus

anthracis)

Limited: wall and

floor surfaces, small

areas, non-sensitive

equipment, personnel

protective equipment,

furnishings (nonfabric)

Potentially effective

decontaminant for

chemical agents in

military and industrial

applications; easy to

apply. EPA issued a

FIFRA crisis exemption

for two foams derived

from the Sandia formulation, but these were later

withdrawn when one of

the technologies failed to

pass EPA’s AOAC

Sporicidal Activity Test. 

EPA has not received or

reviewed data for Decon

Green under FIFRA.
Technology Technical

Maturity

Applicable Agents Scope of Building

Applications

Effectiveness 

5

CASCAD Commercially

available.

Chemical agents:

(nerve and blister)

Biological agents

(Bacillus

anthracis) 

Radiological

containment

Product is not

demonstrated in

buildings but foambased application to

surfaces and walls is

possible. 

Vendor claims removal of

nerve agents within five

minutes of application. 

US test data show

variability in treatment

effectiveness that requires

additional study. EPA has

not received or reviewed

data for CASCAD under

FIFRA.

L-Gel Innovative. 

Nearing

commercialization.

Chemical agents:

(nerve and blister)

Biological agents

(Bacillus

anthracis) 

Gel form will adhere

to vertical and

overhead surfaces. 

Penetrates paint and

varnish. 

Research shows more

than 99 percent effective

for all agents on all

surfaces. EPA has not

received or reviewed data

for L-Gel under FIFRA.

Chlorine dioxide

gas

Mature in a

range of

applications

(medical

sterilization,

water treatment,

oil well treatment).

Commercially

available.

Biological agents

(Bacillus

anthracis) 

Used to fumigate

three sites, ranging in

volume from 90,000

to 14 million cubic

feet, contaminated

with B. anthracis. 

Need to achieve

proper ranges of

temperature, relative

humidity, concentration and exposure

duration to achieve

effective kill rates. 

Must be able to seal

area completely.

Data show six log kill in a

reproducible fashion on

specific surfaces under

controlled conditions in

test chambers or biomedical sterilization units. 

Highly effective in

reducing B. anthracis

spore load in Hart Senate

Office Building, though

further surface treatment

with liquid agent needed. 

In combination with other

decon steps, successful in

remediating the

Brentwood (Washington,

DC) postal facility, since

all post-remediation

environmental samples

were negative. Along

with other steps, also

successful at the Trenton,

NJ, postal facility.
Technology Technical

Maturity

Applicable Agents Scope of Building

Applications

Effectiveness 

6

Hydrogen

peroxide vapor

Mature in

pharmaceutical

applications. 

Commercially

available.

Biological agents Used in pharmaceutical industry to treat

manufacturing clean

rooms and laboratory

animal toxicology

rooms. Used to

fumigate two federal

mail facilities, with

volumes of 1.4 to 1.7

million cubic feet,

contaminated with B.

anthracis spores. 

Both buildings were

sub-divided into

zones no greater than

250,000 cubic feet

each. Zones were

fumigated

sequentially. 

Hydrogen peroxide

vapor interacts with

nylon and with

porous surfaces,

thereby losing

effectiveness.

Documented effectiveness

against viruses, bacteria,

and spores under

controlled conditions. 

Achieved log six kill on

all B. stearothermophilus

biological indicators in all

zones fumigated at GSA

Building 410 and at the

Dept. of State mail annex

SA-32. Special effort

required to maintain H2O2

concentration in SA-32

due to porous surfaces

(e.g., unpainted concrete

block) in the building. 
Technology Technical

Maturity

Applicable Agents Scope of Building

Applications

Effectiveness 

7

Paraformaldehyde Mature in

biomedical lab

applications. 

Commercially

available.

Biological agents Used to decontaminate labs and biosafety

hoods for range of

bio agents, including

B. anthracis. Following 2001 B. anthracis

mail attack, was used

successfully in Dept.

of Justice mail

facility to treat mail

sorting equipment

enclosed within a

tented volume.

Utilized by US Army

Medical Research

Institute of Infectious

Diseases

(USAMRIID) to

decontaminate entire

buildings with high

levels of B. anthracis

contamination. Has

good penetrability of

surfaces. The

fumigant (which is a

Hazardous Air

Pollutant) – and the

byproducts from

reaction of the

fumigant with

organic compounds

on surfaces – might

de-gas from porous

surfaces over a period

of time.

Proven effectiveness in

multiple settings,

including labs, isolated

volumes within buildings,

and, in USAMRIID’s

case, entire buildings. 

USAMRIID regulations

for fumigations of articles

and areas within buildings

stipulates that spore strips

containing 105

 spores of

B. stearothermophilus and

additional spore strips

containing 106

 spores of

B. subtilis var. niger all be

negative for growth of the

spores after fumigation;

otherwise the fumigation

is to be repeated.

Methyl bromide Innovative in

this application. 

Commercially

available for

residential,

agricultural pest

control applications.

Biological agents.

(Has historically

been applied for

insects.)

Testing in a mobile

home showed ability

to kill spores in the

Bacillus family in

difficult-to-reach

areas. A concern is

that methyl bromide

is an ozone depleter,

and no effective

system has yet been

demonstrated for

destroying the fumigant following

fumigation.

In a test trailer, achieved

6-log kill of B. anthracis

surrogates in hard-toreach locations following

a two-day fumigation.
8

Table 1.3-2. Summary of Technology Application Issues

Technology Materials Compatibility Residuals/ Degradation

Products

Additional Hardware

Requirements

Hypochlorite Not compatible with

dyes. Corrosive. Oxidant.

Corrosive nature of

material means that waste

products should be

managed and disposed of

as hazardous waste.

Not applicable. 

Aqueous chlorine dioxide Harmful to fabrics

(oxidant)

Excess aqueous solution

is an oxidant. If gas is

generated on-site to

produce the solution,

byproducts of the

generation process can

include a brine solution,

depending on the process.

Commercial aqueous

ClO2 products can be

imported from off-site,

requiring no additional

hardware on-site. 

Alternatively, aqueous

ClO2 can be produced by

solubilizing ClO2 gas

manufactured on-site

using on-site generators.

Aqueous hydrogen

peroxide

Harmful to fabrics

(oxidant)

None. Breaks down to

water and oxygen after

treatment.

Not applicable.

TechXtract Abrades or dissolves

away treated porous

surface.

Fresh TechXtract solution

is not hazardous,

according to the vendor. 

Waste extract generated

by the use of the product

may contain hazardous

chemicals.

No data.

Sandia Foam and Decon

Green

Bare steel objects are

susceptible to rust after

application. Safe on all

other surfaces, according

to the vendor.

Foam requires removal

and may be contaminated

with removed chemicals.

Uses standard,

commercially available

paint sprayers. 

CASCAD No effect on paint,

rubber, or aluminum,

according to the vendor.

Foam requires removal

and may be contaminated

with removed chemicals.

Uses standard firehoses. 

A backpack version also

can be purchased from

the vendor.

L-Gel No harm to carpet or

paint, according to the

developer.

Silica in gelling material

considerably increases the

amount of waste requiring

management.

Uses standard,

commercially available

paint sprayers. Must use

a metal nozzle due to

corrosivity of L-Gel.

Chlorine dioxide gas Bleaching of selected

fabrics and photographic

materials. 

Wastes will include: a)

wastes from generation of

the ClO2 (e.g., a brine

solution, depending upon

the ClO2 vendor); and b)

wastes from scrubbing the

ClO2 from the fumigated

area prior to aeration

(e.g., a caustic sulfite/

sulfate solution).

Gas is unstable and

cannot be stored in

canisters. A specialized,

potentially sophisticated

gas generation system is

required, which will vary

depending upon the ClO2

vendor. A system will

also be required for

scrubbing the residual

ClO2 from the building air

following fumigation.
Technology Materials Compatibility Residuals/ Degradation

Products

Additional Hardware

Requirements

9

Hydrogen peroxide vapor Not corrosive, but will

discolor dyes and have

unfavorable interactions

with nylon. Porous

surfaces may degrade and

inactivate hydrogen

peroxide vapor.

None. Vapor

introduced/withdrawn

from site in closed system

containing a catalyst on

the return side which

degrades hydrogen

peroxide vapor to water

and oxygen.

Hydrogen peroxide vapor

is produced by heating a

35% solution of hydrogen

peroxide.

Paraformaldehyde No problems reported. Following fumigation, the

formaldehyde (a

Hazardous Air Pollutant)

is scrubbed from the

treated area using, e.g.,

ammonium bicarbonate

prior to aeration. 

Byproducts from this

scrubbing process will be

a waste.

p-Formaldehyde can be

heated on hotplates using

disposable pie tins or by

using a generator system.

Methyl bromide No damage to

photographic, cellulosic,

fabric, or electronic

materials in two

experiments in a trailer.

After treatment, the

methyl bromide must be

scrubbed from the treated

area, and there will likely

be wastes from this

scrubbing process. 

Byproducts from this

scrubbing process will be

a waste. Currently, there

is no treatment to destroy

methyl bromide following

fumigation; in the

experiments performed to

date, it has been released

directly to the

environment.

Liquid under pressure is

heated on-site to create

vapors that are pumped

into the space to be

fumigated.

1.4 Identification of Areas for Potential Research

Table 1.4-1 presents the areas of potential future research identified for each technology as well

as those applicable to all. 
10

Table 1.4-1. Potential Research Areas

Technology Research Areas

Hypochlorite C At what concentration, pH, contact time, or other parameters would

hypochlorite be effective on porous surfaces.? 

C At what concentration, pH, contact time, or other parameters would

hypochlorite be effective on biological agents other than anthrax spores?

Aqueous hydrogen

peroxide

C Field testing is needed to determine treatment effectiveness and operational

variables (e.g., contact time, concentration) towards both chemical and

biological agents.

Aqueous chlorine

dioxide

C Field testing is needed to determine treatment effectiveness and operational

variables (e.g., contact time, concentration) towards both chemical and

biological agents.

TechXtract C Laboratory and field testing of the technology is needed, including destruction

effectiveness, against chemical warfare agents such as VX and GB.

C Testing is needed of treatment effectiveness on nonporous surfaces.

Sandia Foam/ Decon

Green

C Field tests are needed to demonstrate the effectiveness of the technology and the

stability of hydrogen peroxide in “dirty” environments.

CASCAD C Independent verification of manufacturer’s claims is needed.

C Validation is needed of use for initial isolation of contamination.

L-Gel C Verification is required of pending improvements to increase penetration into

porous surfaces and to aerosolize L-Gel for application to interior ventilation

systems. 

C Mechanisms must be studied to minimize the mass of amorphous silica used. 

C Potential for stabilization of waste materials must be studied.

Chlorine dioxide gas C Further research is needed to determine D-values for ClO2 concentrations in

range (750 - 2000 ppm) used for fumigations of three contaminated facilities

C Reliable, rugged, and cost effective real-time monitors for ClO2 concentration

must be developed in the concentration range used for fumigations

C Research is necessary on effectiveness against other biological agents.

C Research is needed on effectiveness against chemical agents.

Hydrogen peroxide

vapor

C Research is needed on materials in buildings which absorb and/or react with

vapor, decreasing effective concentration in space being fumigated.

C Research is needed to develop an improved system for vapor generation

C Feasibility of scaling up technology to fumigate spaces larger than 200,000

cubic feet must be demonstrated.

Paraformaldehyde C The optimal combination of vapor concentration, relative humidity, temperature,

and contact time needed to achieve effective decontamination must be determined.

C Quantification is needed of the effectiveness of treatment on porous surfaces and

difficult to reach areas. 

Methyl bromide C More extensive research is needed on critical process parameters for effective

spore kill; namely, temperature, relative humidity, vapor concentration,

exposure time. 

C A practical system to destroy methyl bromide vapor following fumigation must

be demonstrated, so as not to release it to the environment

Other C A standardized method must be developed for preparation of bacterial and viral

standards for remedial technology validation.

C Effectiveness of using combinations of technologies (i.e., different gas phase

technologies) as a treatment train should be studied.
11

1.5 The NHSRC Decontamination Program to Address these Issues

The NHSRC Safe Buildings decontamination program, designed to address the issues raised

above, to the extent possible, is formulated as follows.

“Lessons Learned”. Extensive practical experience in building decontamination has been

developed during the course of the building remediations that followed the 2001 anthrax mail

attacks. Under the Safe Buildings program, NHSRC will interact with all of the principals

involved in these remediations, compiling the data that were generated and documenting the

practical field experience that was gained. This will enable NHSRC to provide decontamination

guidance to future users that draws, as fully as possible, on the past experiences.

“Systematic Decon”. In a series of controlled experiments, NHSRC will determine how the

performance of alternative decon technologies – liquids, foams and gels, and gases and vapors –

vary as key parameters are varied. The parameters that will be varied include, e.g., the nature of

the CB agent, the substrate on which the agent is deposited (wallboard, carpeting, etc.), the

concentration of the decon agent, the exposure time, the temperature, and the relative humidity. 

Performance measures will include the efficacy of killing biological agents or neutralizing

chemical agents, compatibility of the decon agent with the substrate, and residual degradation

products left on the decontaminated surface. The results from these experiments will address

many of the questions raised in Table 1.4-1, regarding the effectiveness of these decon agents

under various conditions.

Decon Environmental Technology Verification (ETV). NHSRC has established a Decon ETV

program, under which vendors of decontamination technologies can submit their technologies

for independent testing by EPA under a standardized protocol. The results from this ETV testing

will provide EPA and potential users with an increased, independent database on the

performance of these technologies.

Engineering and Economic Analysis. Drawing from the above three projects, a parametric

analysis will be conducted of the practical engineering issues that will have to be addressed, and

the cost-effectiveness of the remediation, for alternative decontamination approaches. The

parameters that will be addressed will include the nature of the CB attack, key variables defining

the building, and key variables associated with each step of the overall remediation process. The

results will be reviewed to determine whether preferred remediation approaches become

apparent for particular building characteristics and attack scenarios.

Decon Technical Guidance Document. The results from all of the tasks above will be brought

together in the development of a user-oriented technical guidance document for building

decontamination. This document would assist building owners and operators, governmental

agencies, remediation personnel, and others in the cost-effective selection and implementation of

remedial action steps in the event of a CB attack on a large building. Once the user has defined

the characteristics of the building and the extent and nature of the attack, the guidance document

would suggest, for example: the extent, methods, and cost of sealing the “hot zone”; the extent

(and costs) of removal of interior furnishings for disposal, prior to further building treatment; the

nature and extent of interior decon (with HEPA vac and liquid agents) prior to fumigation, and

the associated costs; fumigation methods, and cost-effective operating conditions; and the nature

and amounts of wastes requiring disposal.
12

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13

2. INTRODUCTION

2.1 Scope, Purpose, and Summary

Following the events of September and October, 2001, there is increased concern regarding the

possibility of the deliberate introduction of chemical or biological (CB) agents, toxic industrial

chemicals (TICs), or toxic industrial materials (TIMs) into buildings by terrorists. Such an

attack would require effective and prompt efforts to protect building occupants and to

decontaminate the building for re-occupancy. Work on decontamination following CB attacks

has been underway at the Department of Defense (DoD) and other agencies for many years,

often focused on military applications. 

On September 24, 2002, the EPA Administrator announced the formation of EPA's National

Homeland Security Research Center, headquartered in Cincinnati, Ohio. The Center, as part of

the Office of Research and Development (ORD), manages, coordinates, and supports a wide

variety of homeland security research and technical assistance efforts. Research at the Center

will focus on developing methods to: 1) protect building occupants during a CB attack, and to

decontaminate contaminated buildings following the attack (including proper disposal of

contaminated waste materials); 2) protect the nation's drinking water supply; and 3) improve risk

assessment techniques. Research on homeland security will develop the scientific foundations to

provide decision-makers with increased understanding and tools necessary to prevent or manage

a range of potential treats.

This document is intended provide background information on potential post-attack building

decontamination technologies, as an aid to EPA in planning their program and as an educational

tool for other users. The document critically analyzes the general knowledge and primary

references regarding commercial and near commercial technologies for decontamination of

surfaces contaminated with CB agents, TICs, and TIMs. This document is intended for

educational purposes. As such, it provides an overview of selected technologies, discusses the

available data and efficacy, and highlights potential research needs. 

2.2 Summary of Decontamination Technologies Selected for Evaluation

The starting point for identification of technologies was the Review of Decontamination

Technologies for Biological and Chemical Warfare Agents (Mitretek, 2003) prepared by

Mitretek for EPA, which provided an overview of potential remediation technologies and

included a literature review. Other primary sources consulted were the DoD Wide Area

Decontamination Study (Battelle, 1999), materials from the EPA Technology Innovation Office

(TIO), and other readily available references. A list of potential technologies, shown below, was

developed. 

Surface-Applied Technologies

C Hypochlorite

C Aqueous hydrogen peroxide

C Aqueous chlorine dioxide

C HPO2® (enhanced aqueous H2O2)

C Decontaminating Solution 2 (DS2)

C TechXtract®

C Nanoemulsions

C Enzymes

C Sandia Foam and Decon Green

C CASCAD®

C L-Gel
14

Gas- and Vapor-Phase Technologies

C Ethylene oxide

C Chlorine dioxide gas

C Hydrogen peroxide vapor

C Paraformaldehyde

C Ozone

C Methyl bromide

 

Other Technologies

C Directed energy

C Photochemical 

C Plasma

A brief synopsis of the potential for use of the technology in a building remediation application

was drafted and formed the basis for determining the technologies to be included in this

document. A summary of the determination on each technology is presented below. 

2.2.1 Surface-Applied Technologies Considered

Surface applied technologies include liquids and foams or gels. Liquid technologies involve the

application of liquid decontamination solutions directly on a surface contaminated with a

biological or chemical agent. Eight technologies are evaluated in this category – hypochlorite

(e.g., bleach), aqueous hydrogen peroxide, aqueous chlorine dioxide, HPO2, DS2, a proprietary

technology called TechXtract, and nanoemulsions. With these technologies, the solution is

applied to the surface of the material to be decontaminated. The solution is removed by wiping

or wet vacuuming.

Foam and gel technologies are designed to enhance surface removal of biological or chemical

contaminants by delivering the decontamination formulation in a matrix that can be applied to

vertical and horizontal surfaces. This allows the application to walls with sufficient contact time

to ensure that the CB agent is effectively treated. In this category, three technologies are

evaluated – Sandia Foam and Decon Green, CASCAD, and L-Gel.

Hypochlorite: Historically, chlorine-based decontamination systems have been effectively

employed against chemical and biological agents. The use of hypochlorite solutions (aqueous

and non-aqueous) or solid/slurry hypochlorites has been wide spread for military applications. 

Hypochlorite is a standard decontaminant in military applications, excluding shipboard use. 

This general purpose decontaminant has been used on personnel, equipment, clothing, building

surfaces, and soil. It is relatively easy to obtain and inexpensive. While an effective

decontaminant, it is corrosive, can form toxic by-products, and has irritant properties that are

undesirable. The military typically uses HTH (high test hypochlorite) and STB (super topical

bleach), along with household bleach solutions, for agent spills and personnel decontamination. 

In addition, EPA evaluated data on one hydrogen peroxide and four hydrogen peroxide/peracetic

acid mixtures. Based on efficacy at contact times ranging from 10 to 30 minutes, EPA issued a

crisis exemption for the use of these products on building surfaces. Because of the wide
15

experience in its application and its commercial availability, this technology was further

evaluated in this report.

Aqueous hydrogen peroxide: There are several sterilization products on the market which

contain hydrogen peroxide. These have applications in the food and medical industries for

general hard surface cleaning of biological organisms as well as food preparation. Additionally,

there are specialized formulations available which have been developed specifically for building

or warfare decontamination. Because of the potential for application to building decontamination, this technology is evaluated further in this report. 

Aqueous chlorine dioxide: As a biological sterilizer, chlorine dioxide (ClO2) is an oxidant for

biological organisms and the exact method of destruction is not known. Unlike Chlorine (Cl2),

chlorine dioxide is a single-electron transfer-oxidizing agent and does not react with organics to

form harmful chlorinated products such as trihalomethane and chloramines. Chlorine dioxide

has extensive use in drinking water treatment, generated from sodium chlorite and fed into the

water. Sodium chlorite-based cleaners are used in the food processing industry for cleaning of

surfaces and of food itself. EPA has data showing the efficacy of aqueous chlorine dioxide

against Bacillus spores on hard, non-porous surfaces when applied at a concentration of 500 ppm

for a 30-minute contact time. A crisis exemption for use of this agent against B. anthracis on

building surfaces was issued by EPA on the basis of these data. This technology has the

potential for application in buildings and is commercially available. As a result, it is further

evaluated in this document. 

HPO2®: EAI Corporation patented a variation of the aqueous hydrogen peroxide system called

HPO2, in which hydrogen peroxide is added to Oxone®. The technology is reported to work for

bulk treatment of chemical agents. Variants of hydrogen peroxide have promise, but no data

could be located on this technology. Further, its commercial availability is unknown. As a

result, this technology was not addressed in this report.

DS2: DS2 is recognized as the military bench mark for effective chemical and biological

decontamination. DS2 was developed to destroy VX and reacts with G agents and mustard gas

at ambient temperatures. It is a mixture of 70 percent diethylenetriamine (DETA), 28 percent

ethylene glycol monomethyl ether (also known as 2-methoxyethanol), and two percent sodium

hydroxide (NaOH). The sodium hydroxide reacts with 2-methoxyethanol to form ethoxide. As

DETA is added, free sodium radicals are bound in the mixture. DS2 is highly reactive, yet stable

in storage under a broad range of temperatures and times. DS2 is no longer manufactured and is

not used at chemical agent destruction facilities because of its corrosive nature to rubber, paint

and plastics and its environmental effects. Sorbents, enzymatic foams, other foams, oxidative

and reactive formulations, and BX24 (a powder that is mixed with water) are under investigation

as replacements. Because replacements for DS2 are being actively investigated and DS2 is

recognized to have corrosive properties, it was not evaluated in this report. 

TechXtract®: TechXtract is designed to remove organics, heavy metals and radionuclides from

the surface and subsurface of porous and nonporous solid materials such as concrete,

brick, wood, and steel. Active Environmental Technologies, Inc. calls TechXtract a

"contaminant extraction technology." The technology uses proprietary chemical mixtures to

treat surfaces including floors, walls, ceilings, and equipment. The mixtures may include macro-
16

and micro-emulsifiers, buffered organic and inorganic acids, and hydrotropic, electrolyte,

flotation, wetting, and sequestering agents that extract the contaminants and bring them to the

surface. The chemical mixtures are applied sequentially, in successive cycles. Each treatment

cycle includes application, penetration, and extraction. Wet vacuuming is used to remove the

solutions from the treated substrate. This low-tech, but innovative, aspect of the technology is

an important element of its effectiveness for porous substrates. Effective decontamination of a

porous surface will be one of the more challenging aspects of building decontamination. 

TechXtract is effective for porous surface decontamination because wetting agents are used to

increase permeation into pores and wet vacuuming is used to get treatment solutions back out of

pores. While effective on porous surfaces, some abrasion or dissolution of the surface occurs.

The proprietary mixtures may include fluorides or other chemicals that present worker health

and safety issues. Because TechXtract was tested and demonstrated in hazardous waste building

remediation, it was selected for further evaluation in this document. 

Nanoemulsions: A generic nanotech emulsion is a mixture of detergent, buffer, oil and water. 

The combination is emulsified and stable for many months. This material is not toxic and can be

applied to personnel as well as equipment. Current applications require manual application, but

the technology could be modified for spraying for wide application. Nanotech emulsions are

reported to be effective against both chemical and biological agents. Nanotech technologies

under development include a line of virus and pathogen Nanofilters® developed by US Global

Nanospace for use in aircraft and buildings. However, nanotech emulsions are in the early

development stages with additional research still underway. While the technology shows

promise, its near term applications are limited, and it was not evaluated for building remediation

applications. 

Enzymes: Enzymatic systems are reported to have been developed and tested successfully

against chemical agents. Researchers at Edgewood Chemical Biological Center are actively

engaged in these efforts. They identified and characterized enzymes that are effective against

chemical and biological agents and cloned the enzymes’ genes. These enzymes decontaminate

chemical and biological agents through catalysis. The researchers developed a powder form of

the enzymes that requires the addition of water for decontamination. The powders are designed

to attack specific contaminants, such as VX and mustard gas. This technology shows promise

but is at the research stage. At the current time, little data on these systems with respect to

building decontamination are available; additional information would be needed to consider this

emerging technology. Further, the technology is not yet in commercial production. As a result,

this technology was not addressed in this report.

Sandia Foam/Decon Green: Peroxide-based systems are one of the more visible chemical

agent decontamination systems in the market today. Sandia National Laboratories developed

“Sandia Foam,” which is marketed under the trade names EasyDecon® and Modec Decon

Formula (MDF) 200®. The Sandia foam uses a combination of surfactants and oxidizers to

inactivate both biological and chemical agents. Edgewood Chemical Biological Center patented

a similar system called Decon Green. These systems are claimed to be effective against all

chemical agents, be easily applied, and not produce toxic residues or byproducts. Both Sandia

and the West Desert Test Center at Dugway Proving Ground have reported six-log kills of

Bacillus anthracis spores within one hour. EPA issued a crisis exemption for the use of these

foams in building remediation for B. anthracis. These were later withdrawn when, in separate
17

testing conducted by EPA under the Federal Insecticide, Fungicide, and Rodenticide Act

(FIFRA), one of the foams did not pass testing to be listed as a sterilizing agent for B. anthracis. 

Because these technologies have potential, they were selected for further evaluation in this

document.

CASCAD®: The Canadian Aqueous System for Chemical Agent Decontamination (CASCAD)

is a chlorine-based system that delivers an aqueous foam designed to contain and eliminate

chemical and biological warfare agents and remove radioactive particle contamination. The

immediate isolation and containment of the contamination is its most significant advantage. The

active decontaminating ingredient is sodium dichloroisocyanurate (fichlor). Fichlor is used

extensively in the food and beverage industry as antibacterial detergent. CASCAD has been

tested in Canada, the U.S., and the U.K. For surface decontamination, the biodegradable foam is

easily applied and sticks to vertical surfaces. CASCAD is intended for exterior applications on

tanks and military equipment. Its use on building interiors has not been tested. Because there is

a body of data on decontamination of biological agents, CASCAD is being evaluated as a

building remediation alternative. 

L-Gel: Lawrence Livermore National Laboratories has developed the L-Gel system using

Oxone®, with fumed silica as a gelling agent. Oxone is a non-chlorine alternative used as a

decolorizer and disinfectant. The active ingredient in Oxone is potassium peroxy monosulfate,

KHSO5. Similar in formulation to the Sandia Foam, this material combines oxidants with

surfactants to destroy biologicals by disrupting the lipid component. Oxone has been shown to

effectively react with chemical agents. Mechanisms for inactivation of chemical agents are less

well known, but the compound is effective against both classes of agents. L-Gel can penetrate

polymeric coatings such as paint and varnish. It is relatively inexpensive (about $1 for materials

only to treat 1 square meter). However, L-Gel is not commercially available (although licensing

discussions are underway). Additionally, the silica gelling agent increases the amount of waste

requiring management after remediation. However, because of its potential applicability to both

chemical and biological agents and its near-term commercial production status, this technology

is further evaluated in this report. 

2.2.2 Gas- and Vapor-Phase Technologies Considered

Gas and vapor phase technologies require that the area to be contaminated be completely sealed

to prevent the escape of the gas or vapor. This may require tenting the entire structure, or 

comprehensive sealing of shell openings throughout the entire building (or in a particular zone

that is to be treated within a larger building). The gas or vapor is injected into the sealed area

and allowed to remain in place for the period of time required to ensure treatment. Gas and

vapor technologies are more susceptible to variations in temperature and humidity than liquid

and foam and gel technologies. Therefore, ways to control these variables must be considered. 

Five gas and vapor phase technologies were considered – ethylene oxide, gaseous chlorine

dioxide, hydrogen peroxide vapor, paraformaldehyde, ozone, and methyl bromide.

Ethylene oxide: Ethylene oxide, an odorless gas at room temperature, can be used for in several

applications, including walk-in sized chambers. It is widely used in hospital and biomedical

sterilization applications because it is highly penetrating. Off-site ethylene oxide chambers were

used for the successful sterilization of critical items for re-use, during anthrax remediation
18

efforts on Capitol Hill and in other federal mail facilities as well as at the National Broadcasting

System (NBC) offices in New York City. Ethylene oxide is a highly reactive molecule with

vapors that are flammable and explosive. As little as three percent ethylene oxide in air can be

flammable (NIOSH, 1994). Toxicity data indicate that ethylene oxide is irritating to the skin,

eyes, and mucous membranes of respiratory tract. Toxicity data indicate that acute exposure to

ethylene oxide can cause nausea, vomiting, and death. Chronic exposure can cause irritation of

eyes, skin, and mucous membranes, cataracts, and problems in brain function. Exposure to

ethylene oxide may result in lung, liver, and kidney damage (U.S. Department of Health and

Human Services, 1993). Ethylene oxide is rated as a Group B1 (probable) human carcinogen. 

Health concerns for subsequent off gassing resulted in an additional heating step to aid in the

release of ethylene oxide from the critical items treated during the remediation efforts in

Washington, D.C. and New York City. Due to the human health issues and the flammability of

ethylene oxide – limiting its use to carefully controlled chambers – this technology is felt to have

no applicability for the fumigation of buildings, other than possible use off-site for sterilization

of critical items. Hence, it was not evaluated in this study.

Chlorine dioxide gas: Chlorine dioxide was discussed earlier under surface applied (aqueous)

technologies. Here, chlorine dioxide is considered in its gaseous form. The chlorine dioxide gas

must be generated on site where remediation occurs using commercially available generators due

to the instability of the gas. Gas replacement during remediation is required due to the

instability. However, this instability has a benefit in that the gas rapidly decomposes after

treatment. The gas has better penetrability than hydrogen peroxide vapor, and thus may more

likely be effective on porous surfaces, although this has yet to be demonstrated. Temperature

and humidity need to be controlled; effective performance may be very difficult to achieve if the

relative humidity drops below 60%. Because this technology was employed successfully for the

remediation of the Hart Senate Office Building and the Brentwood (Washington, D.C.) and

Trenton, New Jersey, U.S. Postal Facilities, it is further evaluated in this report. 

Hydrogen peroxide vapor: Hydrogen peroxide vapor is used to treat pharmaceutical

manufacturing clean rooms and laboratory toxicology rooms. Hydrogen peroxide vapor was

used in the remediation of two federal mail facilities following the 2001 incident. It was

demonstrated to be effective against Bacillus spores, including the anthracis strain. This

technology is mature and commercially available. Because of its use in building remediation,

this technology is further evaluated in this report.

Paraformaldehyde: Paraformaldehyde is used for routine decontamination of labs and

biosafety hoods in clinical and research laboratories for a broad spectrum of biological agents,

including Bacillus anthracis spores. Paraformaldehyde is heated to generate formaldehyde gas

for use as a sterilizing agent. This gas has been used by the U.S. military for the successful

remediation of numerous laboratories and buildings. Formaldehyde is an animal carcinogen and

probable human carcinogen, and it is genotoxic in a number of assays. This technology is

mature and commercially available. Because it has been used by the U.S. Army Medical

Research Institute of Infectious Diseases to decontaminate buildings, and was used for treating a

mail processing machine in the Department of Justice mail room following the 2001 B. anthracis

mail attacks, it is further evaluated in this report.
19

Ozone: Ozone is a reactive form of oxygen that is a strong oxidant with documented ability to

kill spores, bacteria and viruses. Ozone generation systems are commercially available. 

However, ozone has not been used for remediation of buildings. While this technology is

promising and could be considered for further evaluation in the future, it is not further evaluated

in this report.

Methyl bromide: Methyl bromide is approved for use as a pesticide under controlled

conditions. Its most common use is to kill termites in buildings, and in soil treatment for

agricultural pest control. Recent demonstrations show its potential for killing Bacillus spores. 

As a result, the technology is further evaluated in this report. However, methyl bromide is an

ozone-depleting compound. In addition, it has potential human health effects. It has cumulative,

delayed effects on the central nervous system, which may appear as long as several months after

exposure. High concentrations can produce fatal pulmonary edema. Chronic exposure can

cause central nervous system depression and kidney injury. It may cause severe and permanent

brain damage. Severe neurological signs may appear when there is a sudden exposure to high

concentrations following continuous slight exposure. Methyl bromide has practically no odor or

irritating effects and therefore no warning, even at hazardous concentrations (EPA, 2003).

2.2.3 Other Technologies Considered

Directed energy alternatives: Directed energy methods for decontamination, such as electron

beam, x-ray, gamma ray, ultra violet radiation, and microwave radiation, have all been

demonstrated to disinfect surfaces. As energy transfer methods, all of these systems can kill

bacteria, bacterial spores, and viruses, given sufficient time and power. However, their use for

building remediation is questionable. While technically possible, it is probably not reasonably

feasible. Two of the major concerns are shadowing and control of the directed energy. 

Contamination within a building will most likely spread to multiple surfaces, many of which

might not be easily accessible to directed energy approaches. While penetrating energy such as

electron beam, gamma, and x-rays might overcome many of the shielding issues, their cost and

secondary damage when applied to buildings could make them undesirable alternatives. As such

these technical alternatives were not reviewed in this document.

Photochemical: Clean Earth Technologies, LLC, located in St. Louis, MO, has developed the

Electrostatic Decontamination System (EDS) for the Technical Support Working Group

(TSWG). Their two step process works on both biological and chemical agents. The EDS is

configured with a photosensitizer sprayer unit (pressurized or battery powered), a photosensitizer

(PS) storage unit, and a light source unit (210 – 310 nm UV light source) for activation. The unit

weighs under 50 pounds and is contained on a cart for portability. Clean Earth Technologies

claims the system is effective at rapidly neutralizing chemical agents and toxic industrial

chemicals (TICs) to levels below their Immediately Dangerous to Life and Health (IDLH)

concentrations, as well as disinfecting biological agents. The photosensitizer is sprayed onto the

surface from a distance of 24 inches, and the UV light can reportedly then decontaminate

approximately 1,000 square feet of surface area in 15 minutes. The system has been tested on

vertical, horizontal, porous, and non-porous surfaces. The photosensitizer solution is claimed

have a shelf life of 10 years and is non-corrosive. This technology is still subject to research and

is not commercially available. As a result, this technology was not further evaluated in this

report.
20

Plasma: Plasmas can be generated at atmospheric pressures for the destruction of biological

organisms. By passing energy through air, the molecules are ionized generating both positively

and negatively charged reactive species. The interaction of these ions, along with the associated

ultraviolet light, kills the microorganisms. This technique is applicable to the cleaning, and

perhaps disinfection, of small areas and electronic equipment. Because of the relatively labor

intensive method of employment and its questionable activity on spores, it was not considered as

a candidate for technical evaluation for building remediation alternatives.

Physical Technologies: There are time-tested, proven technologies for physical remediation of

chemical spills. For example, there are a variety of sorbent materials (simple, reactive and

catalytic) on the market for spot surface decontamination. However, after use, the contaminated

sorbent must be recovered and removed for treatment. Hot air and steam jet systems can also be

considered as physical removal systems for chemical threat agents. But the chemical agent that

is thus driven from the surface must be collected and subsequently treated. This report does not

cover the standard spill remediation solutions that a responder may need to include in a

remediation effort. At sufficient temperature and exposure time, heat and steam have long been

utilized for killing biological organisms; however, the temperatures involved are probably too

high for practical use in a building. These technologies are not evaluated here.

2.3 Broad Review of Categories of Alternatives with Potential Applications

Based on the comparative analysis described in Section 2.1, eleven technologies were selected

for analysis. The technologies presented in this document include:

Liquid systems Foam/gel systems

C Hypochlorite • Sandia Foam and Decon Green

C Aqueous chlorine dioxide • CASCAD

C Aqueous hydrogen peroxide • L-Gel

C TechXtract

Gaseous and vapor systems

C Chlorine dioxide gas

C Hydrogen peroxide vapor

C Paraformaldehyde

C Methyl bromide

An overview of these technologies was presented in Section 1. 

In Chapters 3, 4, and 5, the technologies are discussed in detail. For each technology evaluated,

a description of the technology is presented, along with an assessment of its technical maturity

and an evaluation of the existing data. To the extent possible, efficacy data are supplemented by

information and data on material compatibilities, residuals generated, and hardware

performance. The current uses of the technology outside building remediation are discussed, and

information regarding user concerns, such as health and safety concerns, is addressed. Finally,

the advantages and disadvantages of each technology is discussed and future research areas are

identified. 
21

As discussed in Section 2.2, some technologies were not selected for evaluation in this report. 

The determination not to evaluate a technology does not imply that the technology is not

effective. In many cases, the outlook for these technologies appears to be quite favorable. 

However, at this time, they generally are not close enough to commercialization (nanotech

nanoemulsions, enzymes, photochemical systems), present human health hazards (ethylene

oxide), or are untested in building applications (ozone, plasma, directed energy). As a result,

they are not covered in this document.

2.4 References for Section 2

Battelle Memorial Institute, 1999. Wide Area Decon: CB Decontamination Technologies,

Equipment and Projects–Literature Search and Market Survey. Report Number AFRL-HE-WPTR-2002-0054. U.S. Air Force Research Laboratory, Washington, DC. March 1999 (Available

For Official Use Only) 

Mitretek Systems, 2003. Review of Decontamination Technologies for Biological and Chemical

Warfare Agents In Support of the U.S. Environmental Protection Agency’s Safe Buildings

Program. U.S. EPA. Washington, DC. March 2003. Draft, not released to the public. 

NIOSH, 1994. NIOSH Pocket Guide to Chemical Hazards. U.S. Department of Health and

Human Services. Washington, D.C. June 1994. 

U.S. Department of Health and Human Services, 1993. Hazardous Substances Data Base. 

National Toxicology Program, National Library of Medicine, Bethesda, MD. 1993. 

EPA, 2003. Chemical Emergency Preparedness and Prevention. EPA Chemical Profile: Methyl

Bromide. U. S. Environmental Protection Agency.

http://yosemite.epa.gov/oswer/CeppoEHS.nsf/Profiles/74-83-9?OpenDocument. Accessed

October 2004.
22

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23

3. LIQUID-BASED TECHNOLOGIES

3.1 Hypochlorite

3.1.1 Technology Description

Historically, chlorine-based decontamination systems have been effectively employed against

chemical agents. The use of hypochlorite solutions (aqueous and non-aqueous) or solid/slurry

hypochlorites has been widespread for military applications. This general purpose

decontaminant class has been used on personnel, equipment, clothing, building surfaces, and

soil, as shown in Table 3.1-1. While an effective decontaminant, its corrosive properties,

formation of toxic by-products, and irritant properties are undesirable. The military typically

uses HTH (high test hypochlorite) and STB (super tropical bleach) along with household bleach

solutions for agent spills and personnel decontamination. The compositions of these materials

include oxides which assures high pH in aqueous solution and provides a hydrolysis reaction for

additional decontamination.

Table 3.1-1. Hypochlorite Decontaminants

Decontaminant Composition Application

Bleach* 2-6% NaOCl in water skin and equipment

HTH (high test hypochlorite)* Ca(OCl)Cl + Ca(OCl)2 as a solid

powder or a 7% aqueous slurry

equipment and terrain

STB (super tropical bleach)* Ca(OCl)2 + CaO as a solid powder

or as a 7, 13, 40, and 70 wt%

aqueous slurries

equipment and terrain

Dutch powder Ca(OCl)2 + MgO skin and equipment

ASH (activated solution of

hypochlorite)

0.5% Ca(OCl)2 + 0.5% sodium

dihydrogen phosphate buffer +

0.05% detergent in water

skin and equipment

SLASH (self-limiting activated

solution of hypochlorite)

0.5% Ca(OCl)2 + 1.0% sodium

citrate + 0.2% citric acid + 0.05%

detergent in water

skin and equipment

* Currently used by DoD

Bleach

Sodium hypochlorite. An aqueous solution of sodium hypochlorite, NaOCl, is often used as a

general purpose decontaminate. Improvements in the effectiveness of the hypochlorite reaction

have been achieved by introducing stronger oxidants to the system. Developed in the 1940's,

calcium hypochlorite (solid) [Ca(OCl)2], STB, and HTH are found to be more effective

decontaminants over a broader range of pH. More recently, in the early 1990's, the U.S. Army

evaluated the application of hydantoin (specifically dichlorodimethylhydantoin, DCDMH) as an

alternative reactant for chemical destruction of chemical agents. The chlorinating power of

DCDMH is greater than that of HTH and STB, and has been used successfully to detoxify

mustard, nitrogen mustard, lewisite, and phosgene. However, reaction mechanisms are similar

to hypochlorite, producing the same decomposition products. The exact reaction mechanism of

DCDMH has not been fully developed.
24

Calcium hypochlorite. Ca(OCl)2 is a powerful oxidizing agent, and is an active component of

both STB and HTH. The hypochlorite ion (OCl–

) generated by an aqueous solution of Ca(OCl)2

is effective in the decontamination of G-agents [Sarin (GB), Soman (GD), Tabun (GA)], VX [Oethyl-S-(2-diisopropylaminoethyl)methylphosphono-thioate] in acidic solutions, and HD [sulfur

mustard, bis(2-chloroethyl)sulfide]. Hypochlorite ions in high pH (basic) solutions are not very

effective in the decontamination of VX for reasons including: 1) reduced solubility; 2) factor of

10 mole excess; and 3) generation of toxic byproducts. The detoxification of HD by

hypochlorite is a simple process that forms several different products. Both sulfoxide (one S-O

double bond) and sulfone (two S-O double bonds) species are formed, each of which undergo

elimination reactions to form monovinyl and divinyl sulfoxides and sulfones. It was found that

VX reacts with OCl–

 ions at low pH (acidic). However, at high pH, the solubility of VX is

greatly reduced, and a greater than 10:1 ratio of active chlorine to VX is required to oxidize VX

as compared to a 3:1 ratio under acidic conditions. In the detoxification of VX, the P-S bond is

broken and P-O, S-O, and S=O bonds are formed. When Ca(OCl)2 dissolves, the result is a

solution that also contains hydroxide ions. The hypochlorite behaves as a catalyst in a

detoxification of G agents by the hydroxide ion.

High Test Hypochlorite (HTH®). The first commercial high-assay calcium hypochlorite product

marketed in the U.S., HTH is a solid powder consisting of calcium hypochlorite, and is a

powerful oxidizing agent. The hypochlorite ion (OCl–

) generated by an aqueous solution of

Ca(OCl)2 is effective in the decontamination of G agents, VX in acidic solutions, and HD. 

Hypochlorite ions in high pH solutions are not very effective in the decontamination or

detoxification of VX for a variety of reasons.

Super tropical bleach (STB). STB is a combination of a powerful oxidizers, calcium

hypochlorite, Ca(OCl)2, and a strong base, calcium oxide, CaO. STB is effective in the

decontamination or detoxification of HD, G agents and VX. The hypochlorite ion (OCl–)

generated by an aqueous solution of Ca(OCl)2 and the hydroxide ion formed by the dissolution

of CaO [which produces Ca(OH)2] is effective in the decontamination or detoxification of G

agents, VX in acidic solutions, and HD. Hypochlorite ions in high pH solutions are not very

effective in the decontamination of VX for a variety of reasons. 

3.1.2 Technical Maturity

Sodium hypochlorite (standard bleach) is the most effective disinfectant for industrial

applications, swimming pools, and household cleaning. Its production is based on very pure

chlorine gas and high quality caustic soda (lye). Similar to chlorine, sodium hypochlorite was

initially used as a bleaching agent in the textile industry.

The principal form of hypochlorite produced, sodium hypochlorite (NaOCl), is used as an

aqueous solution (Kirk-Othmer, 1992). Sodium hypochlorite was first registered for use in the

United States as an antimicrobial pesticide in 1957 (EPA, 2004). Sodium hypochlorite has

proven to be effective against a wide range of bacteria, fungi, and viruses. It is registered by the

EPA for use in the sanitization and disinfection of household premises, food processing plants,

and agricultural settings. It is also used in animal facilities, hospitals, human drinking water

supplies, chemical pulp and textile bleaching, as a commercial laundry and household bleach, as

a sanitizer for swimming pools, and as a disinfectant for municipal water and sewage (Kirk-
25

Othmer, 1993; EPA, 2004). Sodium hypochlorite solutions are sold for household purposes at 5-

6 percent concentrations, while 10-15 percent concentration solutions are sold for swimming

pool disinfection, institutional laundries, and industrial purposes (Kirk-Othmer, 1992).

In food processing, sodium hypochlorite is used as a disinfectant and sanitizer (Kirk-Othmer,

1993). NaOCl may be used in washing and lye peeling of fruits and vegetables, and both sodium

and calcium hypochlorite may be used as a final sanitizing rinse on food processing equipment

(EPA, 1991). Hypochlorite is still used in pulp bleaching, but its use is decreasing because the

bleaching reaction generates chloroform (Kirk-Othmer, 1992).

Synonyms and trade names for sodium hypochlorite include Clorox®, bleach, liquid bleach,

sodium oxychloride, Javex®, antiformin, showchlon, Chlorox, B-K, Carrel-Dakin solution,

Chloros, Dakin's solution, hychlorite, Javelle water, Mera Industries 2MOm3B®, Milton,

modified Dakin's solution, Piochlor®, and 13 percent active chlorine.

Sodium hypochlorite is generally sold in aqueous solutions containing 5 to 15 percent sodium

hypochlorite, with 0.25 to 0.35 percent free alkali (usually NaOH) and 0.5 to 1.5 percent NaCl.

Solutions of up to 40 percent sodium hypochlorite are available, but solid sodium hypochlorite is

not commercially used. Sodium hypochlorite solutions are a clear, greenish yellow liquid with

an odor of chlorine. Odor may not provide an adequate warning of hazardous concentrations.

Sodium hypochlorite solutions can liberate dangerous amounts of chlorine or chloramine if

mixed with acids or ammonia. Anhydrous sodium hypochlorite is very explosive. Hypochlorite

solutions should be stored at a temperature not exceeding 20 /C away from acids in well-fitted

air-tight bottles away from sunlight.

Calcium hypochlorite, Ca(OCl)2, is the principal form of solid hypochlorite produced

commercially. Water treatment is the largest use of calcium hypochlorite. Calcium hypochlorite

was first registered for use as a pesticide in 1957. Calcium hypochlorite (65-70 percent available

Cl2) is used for disinfection in swimming pools, drinking water supplies, and for treatment of

industrial cooling water. Its cooling water applications include slime control of bacterial, algal,

and fungal origin. Calcium hypochlorite is also used for disinfection, odor control, and

biological oxygen demand (BOD) reduction in sewage and wastewater effluents. It is used as a

sanitizer in households, schools, hospitals, and public buildings, and is used for microbial control

in public eating places. Calcium hypochlorite is used for bacterial and odor control, and general

sanitation in many food-related industries including dairies, wineries, breweries, canneries, food

processing plants, and beverage bottling plants (Kirk-Othmer, 1993). High assay calcium

hypochlorite (70-74 percent available Cl2) was first commercialized in the United States in 1928

under the trade name HTH. It is now produced by two additional manufacturers in North

America (Kirk-Othmer, 1993).

Calcium hypochlorite is a white crystalline solid, decomposes at 100°C, decomposes in water

and alcohol, is not hygroscopic, and is practically clear in water solution. It is toxic by ingestion,

skin contact, and inhalation. Calcium hypochlorite is generally available as a white powder,

pellets, or flat plates. It decomposes readily in water or when heated, releasing oxygen and

chlorine. It has a strong chlorine odor, but odor may not provide an adequate warning of

hazardous concentrations. Calcium hypochlorite is not flammable, but it acts as an oxidizer with

combustible material and may react explosively with ammonia, amines, or organic sulfides. It

becomes a dangerous fire risk in contact with organic material. Calcium hypochlorite should be
26

stored in a dry, well-ventilated area at a temperature below 120 /F (50 /C), separated from acids,

ammonia, amines, and other chlorinating or oxidizing agents. 

Synonyms and trade names for calcium hypochlorite include losantin, hypochlorous acid,

calcium salt, B-K Powder, Hy-Chlor®, chlorinated lime, lime chloride, chloride of lime, calcium

oxychloride, HTH, mildew remover X-14®, Perchloron®, and Pittchlor®.

Super tropical bleach was standardized in the 1950s. It is a mixture of 93 percent calcium

hypochlorite and 7 percent sodium hydroxide and is more stable than bleach in long-term storage

and easier to spread (Modec, 2003). This stability makes super tropical bleach useful for

application in hot, humid climates (Kirk-Othmer, 1992).

Sodium and calcium hypochlorite are extremely corrosive, causing severe damage to the eyes

and skin upon contact. Because of these acute effects, they have been assigned to Toxicity

Category I, the highest degree of toxicity, by EPA. Residues of sodium and calcium

hypochlorite that may remain on certain food crops disinfected with the chemicals pose no

known human health hazard (EPA, 1991). 

Due to the acute toxicity of these products, protective clothing, safety glasses or goggles, and

chemical-resistant gloves are required while handling and applying products that contain sodium

or calcium hypochlorite as the active ingredient. Re-entry levels must be met before entering

swimming pools, hot tubs, or spas treated with sodium or calcium hypochlorite, and reentry

intervals must be observed before using food and non-food contact surfaces that have been

sprayed or fogged with either chemical (EPA, 1991).

3.1.3 Applications of the Technology

Chlorine-based aqueous solutions have been considered as general purpose decontaminants since

World War I. Many studies have been performed to evaluate their effectiveness on chemical

agents. Chemical oxidation is applicable to the decontamination process. The reaction

chemistry is very complex and varies between the different chemical agents. The reactions

process is highly dependent on the pH of the solution, solubility of the agent, and competing

hydrolysis reactions producing undesired reaction products in some cases. 

The requirement for chemical agent decontamination dates back to World War I when Germany

unleashed HD on Allied troops at Ypres, France in 1915. Prior to that time, the poisonous

chemicals used on the battlefield, such as chlorine, were non-persistent gases and required no

decontamination. The first decontaminants used were bleaching powders and, to a lesser extent,

potassium permanganate. The reactions of chemical agents with excess bleach are so vigorous

that both neat and thickened agents can be converted to less or nontoxic products at the

liquid-liquid (bleach solution) or liquid-solid (bleach powder) interface in a few minutes. 

Solubilization of the agents in the same medium as the bleach is not required. HD is converted

into a series of oxidation and elimination products. It is believed that the sulfoxide is formed

first, followed by sulfone formation. Subsequently, both oxidation products undergo elimination

reactions in the strongly basic solution to produce the corresponding monovinyl and divinyl

sulfoxides and sulfones, although small amounts of additional unidentified products are also

present in the final solution (Yang, 1992).
27

By World War II, superchlorinated bleaches, shown in Table 3.1-1, were used as the most

common general purpose decontaminants. However, there are some disadvantages to using

bleach as a decontaminant: 1) the active chlorine content of the bleach gradually decreases with

time so that a fresh solution must be prepared prior to each use; 2) a large amount of bleach is

required for the oxidation of the agents; and 3) bleach is corrosive to many surfaces.

Common oxidants used for decontamination are bleaches that produce active chlorine. Active

chlorine exists in water in equilibrium with the hypochlorite ion, 3ClO–

 = 2Cl– + ClO3

–

. STB 

[Ca(OCl)2 + CaO] and HTH [Ca(OCl)Cl + Ca(OCl)2], are prepared as slurries that are a mixture

of water and solid bleach powders.

During the remediations of several of the buildings that were impacted by the 2001 anthrax mail

attack, household bleach – diluted 10:1 (to 0.525% to 0.6% NaOCl), and adjusted to a pH near

neutral – was used with apparent success in wiping down surfaces contaminated with B.

anthracis. This application for B. anthracis was authorized by a crisis exemption issued by EPA

under Section 18 of FIFRA, following EPA testing of the pH-modified bleach using the AOAC

Sporicidal Activity Test (AOAC, 2000). Based upon this testing, the crisis exemption specified

that the bleach solution had to be adjusted to a pH near 7, that it be utilized only on hard (nonporous) surfaces, and that the surfaces remain wetted with the bleach solution for no less than 60

minutes. The crisis exemption also required that – following the total remediation process for

these buildings, including the bleach wipe-down step – environmental sampling be conducted

within the treated areas of the buildings to confirm the efficacy of the total procedure. The

results of the sporicidal activity testing are discussed in the following section.

Further discussion of the crisis exemption for the use of bleach against B. anthracis can

be found on EPA’s web site at: 

www.epa.gov/pesticides/factsheets/chemicals/bleachfactsheet.htm.

3.1.4 Compilation of Available Data

Chemical agents. The U.S. Army’s Field Manual 3-9 recommends the use of hypochlorite for

decontamination of chemical agent spills and equipment clean up (U.S. Army, 1990). Field

Manual 3-5, NBC Decontamination (U.S. Army, 2002), lists STB and HTH as standard

decontaminants, and bleach as a non-standard decontaminant. STB and HTH are not

recommended for ship use, whereas bleach is.

Laboratory studies have documented that aqueous solutions of hypochlorite can successfully

eliminate chemical agents (HD, GB, GD, GA, and VX) below 1 part per million with reaction

half lives of 1.5 minutes or less (Yurow, 1991). 

G agents can be rapidly detoxified in bleach solutions. The hypochlorite anion behaves as a

catalyst breaking the P-F bond in GB and GD (and P-CN bond in GA), substituting a hydroxyl

group to the P atom and releasing the fluoride (or cyanide) ion (Epstein, 1956). The elimination

of the fluoride (or cyanide) creates a less toxic phosphono compound.

Bleach can also be used for the decontamination of VX, particularly under low pH conditions. 

VX readily dissolves in acidic solutions via protonation of the nitrogen while the sulfur is

oxidized by HClO. Under such acidic conditions, only three moles of active chlorine are
28

consumed for each mole of VX. At high pH, the solubility of VX is significantly reduced. The

non-protonated nitrogen is oxidized, accompanied by the evolution of chlorine or oxygen gas

and the formation of sulfate and carbonate salts. Under basic conditions, more than 10 moles of

active chlorine are required to oxidize 1 mole of VX. Despite the long history of alkaline bleach

solutions as general purpose decontaminants for the chemical agents, the precise stoichiometry at

high pH has not been determined for VX (Yang, 1992). 

Biological agents. Decontamination of biological simulant (bacillus subtilis var. niger, known

as Bg) with sodium hypochlorite was reported in a Battelle report (Battelle, 1999). The

effectiveness of three decontaminants was compared. The decontaminants were: 1) pH-adjusted

sodium hypochlorite (ASH) composed of household bleach (5.25 percent by weight), white

vinegar for pH adjustment (5 percent acid strength), and dilution water; 2) diluted bleach (5.25

percent by weight sodium hypochlorite), diluted with water; and 3) plain water. The results

(Table 3.1-2) indicate that ASH was the most effective decontaminant against the Bg, effectively

reducing the spore count by 99.6 percent.

The conclusions reached from this study were: 1) ASH performed better than either diluted

bleach or plain water; 2) the presence of dirt, mud, and foreign material will greatly reduce the

germicidal power of ASH; and 3) the decontamination process is limited to small areas and

easily reachable locations. Subsequent studies report that hypochlorous acid (2.5 percent

aqueous solution) had a 100 percent Bg spore kill rate at relative humidity (RH) of 100 (CBIAC

and AD - A084392, as referenced in Battelle, 1999). 

Table 3.1-2. Residual Agent after Decontamination

Decontamination

Solution

Sample # Total Spores on Strip After

Spray

Average Percent

Reduction

Water 1 8.9 x 104 96.8

2 6.2 x 104

3 3.6 x 104

Bleach 1 4.5 x 104 98.0

2 4.0 x 104

3 4.0 x 104

ASH 1 1.1 x 104 99.6

2 5.3 x 103

3 5.6 x 103

Diluted sodium hypochlorite was tested by EPA for its sporicidal activity following the 2001

anthrax mail attacks, to support a crisis exemption under FIFRA that would allow the use of this

product against B. anthracis spores in some of the affected buildings. Tests were conducted

using the AOAC Sporicidal Activity Test (AOAC, 2000). The product tested was household

bleach (6% NaOCl) that had been diluted with water by a 10:1 ratio, resulting in a 0.525%

solution. Two such dilute solutions were tested: bleach that had been diluted with pure water

(resulting in a pH of 10.2); and bleach that had been diluted with water and with white vinegar,

in order to achieve a final solution pH of 6.5, near neutral. Consistent with the AOAC protocol,

the sporicidal efficacy of these two solutions was tested using two surfaces inoculated with 106

to 107 B. subtilis spores: porcelain penicylinders (representing hard, non-porous surfaces) and

silk suture loops (representing porous surfaces). The AOAC test does not determine the
29

quantitative log kill of the spores; it measures qualitatively whether or not all the spores on the

surface were killed.

The results of the testing on the porcelain penicylinders showed that – with the pHadjusted 0.525% NaOCl – more than 90% of the penicylinders had complete kill after 30

minutes of exposure time, and every cylinder showed complete kill after 60 minutes. By

comparison, the non-adjusted (high-pH) bleach still showed live spores on 40% of the

penicylinders after 30 minutes.

The results of the testing with the silk suture loops showed live spores on essentially all

of the loops, even after 90 minutes of exposure time.

On the basis of these efficacy results, EPA issued a crisis exemption for the use of

sodium hypochlorite solutions in the B. anthracis remediation activities, with the following

provisions: it is for use only on hard surfaces; the solution must be pH-neutral, with a NaOCl

concentration between 0.5% and 0.6%; and the contact time of liquid solution on the surface

must be no less than 60 minutes (with the solution having to be re-applied if the surface dries

prior to that time). Additionally, post-remediation sampling must be performed to confirm that

the remediation process – including the bleach application step, and any other steps that are

performed (e.g., including fumigation) – has in fact been efficacious.

Issuance of a crisis exemption requires that EPA consider the safety of a product, as well

as the product’s efficacy. The Agency’s review deemed this product to be safe for use with

proper protective measures, since it is already registered under FIFRA for other (disinfection)

applications.

3.1.5 Concerns for the User (Applicability)

Calcium hypochlorite is a white, crystalline, and oxidizing solid material which looks much like

table salt. The solid material has a faint odor of chlorine, and can be toxic by ingestion, skin

contact, and inhalation. Calcium hypochlorite is used as a disinfectant in swimming pools,

sewage treatment operations, and in water treatment operations. 

Solid calcium hypochlorite should not be stored near reactive or combustible materials. Fires

involving calcium hypochlorite may be difficult to put out because if calcium hypochlorite is not

kept completely dry, it will decompose liberating oxygen and chlorine. A spontaneous fire or

explosion could result if solid Ca(OCl)2 is not kept dry and is stored with organic or other

flammable material(s). Therefore, calcium hypochlorite must be stored in a completely dry

location, isolated from combustible materials, or fully dissolved to prevent creating a hazardous

condition.

Hypochlorites should be used as aqueous solutions. Contact with organic materials in the dry

form may cause fires or generation of toxic gases. The MSDSs for different forms of bleach and

calcium hypochlorite are available on the web.

3.1.6 Availability of the Technology for Commercial Applications
30

Sodium- and calcium-based hypochlorites are commercially available under a range of brand

names, as discussed in the preceding sections. 

Historically, hypochlorite decontamination solutions have been used to decontaminate biological

organisms in small areas, personal protective equipment, and contaminated floor/ground/wall

surfaces. The systems are "low tech", that is, hand sprayers, buckets, mops, rags, brushes, etc.

are used to apply the solution to the contaminated surfaces with vigorous scrubbing followed by

a water rinse. EPA’s testing using the AOAC Sporicidal Activity Test has shown that diluted

household bleach (NaOCl) is effective in achieving a six- to seven-log reduction in Bacillus

subtilis spores when applied to hard, non-porous surfaces, if the sodium hypochlorite is adjusted

to a pH of 7, and is allowed to contact the surface for 60 minutes. Diluted bleach was not found

to be effective on porous surfaces (silk suture loops) in the AOAC test.

Hypochlorites are also used by the military to decontaminate spills of G and VX chemical

agents. For VX decontamination to be effective, the pH of the bleach must be low.

3.1.7 Advantages and Disadvantages

Hypochlorite solutions are relatively available (household bleach is available in any grocery

store, HTH is available from swimming pool supply and chemical companies), low-cost, and

easy to obtain. The application is low tech and requires little knowledge of equipment operation. 

However, the user must be aware of the dilution, pH adjustment, and contact time requirements

for treatment to be effective, as defined by EPA’s AOAC testing. 

The corrosive nature of hypochlorite solutions requires care to be taken to ensure materials

treated are resistant to the oxidative process. Attention to waste containment and recovery is

required. The waste generated from the use of high-concentration, non-pH-adjusted

hypochlorites should be considered to be hazardous and handled accordingly. However, the

wastewater may be declared non-hazardous if when bleach is used in accordance with the EPA

crisis exemption (i.e., it is diluted to 0.5 to 0.6% NaOCl concentration, and the pH is adjusted

with vinegar to be near neutral).
31

3.1.8 Potential Areas for Future Research (Uncertainties)

Further research is needed to systematically quantify the concentration, solution pH, and length

of contact time required for hypochlorites (in particular, NaOCl) to be effective on a variety of

biological agents (in addition to B. subtilis spores) on both non-porous and porous surfaces. 

Similar testing is needed for the range of hypochlorites, quantifying concentration, pH, and

contact time required for efficacy against chemical agents.

3.1.9 References for Section 3.1

AOAC, 2000. Official Methods of Analysis, 17th ed.: Method 966.04. AOAC International,

Gaithersburg, MD.

Battelle, 1999. Wide Area Decontamination: CB Decontamination Technologies, Equipment,

and Projects--Literature Search and Market Survey. Report to the U.S. Joint Service Materiel

Group by Battelle Memorial Institute and Charles W. Williams, Inc. March 1999.

EPA, 1991. Reregistration Eligibility Document - Sodium and Calcium Hypochlorite Salts,

738-F-91-108.

EPA, 2004. Pesticides: Topical & Chemical Factsheet – Bleach. U. S. Environmental

Protection Agency. www.epa.gov/pesticides/factsheets/chemicals/bleachfactsheet.htm. 

Accessed November 2004.

Epstein, 1956. Epstein J; Bauer, V.E.; Saxe, M.; and Demek, M.M. Journal of the American

Chemical Society, 78: 4068-4071.

Modec, 2003. Formulations for the Decontamination and Mitigation of CB Warfare Agents,

Toxic Hazardous Materials, Viruses, Bacteria and Bacterial Spores. Modec, Inc. Technical

Report MOD2003-1012-G. Issued February 2003.

Kirk-Othmer, 1992. Encyclopedia of Chemical Technology, Fourth Edition, Volume 4,

“Bleaching Agents,” pp. 271-310.

Kirk-Othmer, 1993. Encyclopedia of Chemical Technology, Fourth Edition, Volume 5,

“Chlorine Oxygen Acids and Salts (ClO2, HOCl),” pp. 951-957.

U.S. Army, 1990. Army Field Manual No. 3-9, Potential Military Chemical/Biological Agents

and Compounds.

U.S. Army, 2002. Army Field Manual 3-5, NBC Decontamination.

Yang, Y.-C.; Baker, J.A.; and Ward, J.R. “Decontamination of Chemical Warfare Agents,”

Chem. Review 1992, 92: 1729-1743.

Yurow, H.W., 1981. “Decontamination Methods for HD, GB, and VX, A Literature Survey”.

ARCSL-SP-80032.
32

3.2 Aqueous Chlorine Dioxide

3.2.1 Technology Description

Chlorine dioxide possesses disinfection properties in both its aqueous and gaseous states. The

focus of this section is an evaluation of aqueous chlorine dioxide.

Chlorine dioxide (ClO2) is unstable and therefore must be generated at the use site, typically

using sodium chlorite as a reactant. Aqueous chlorine dioxide is generated for use as a hard

surface cleaner by adding gaseous chlorine dioxide to water. Gaseous chlorine dioxide is

generated via the mechanisms and equipment described in Section 5.1 of this document. Gas

generated in this manner can be subsequently dissolved in water. For example, gas generators

discussed in Section 5.1 can generate both gaseous and aqueous chlorine dioxide.

Aqueous chlorine dioxide can also be generated by acidifying an aqueous sodium chlorite

(NaClO2) solution. So-called “stabilized chlorine dioxide” is a commercially available solution

of sodium chlorite, pH-adjusted to be slightly basic. This basic sodium chlorite forms a chlorine

dioxide solution with the addition of acid, and is thus sold as a ‘two-part’ formulation (Purogene,

2003). However, the apparent instructions for at least one product is to dilute the concentrated

product in water and apply to surfaces (Neways, 2001). In this case, the precise mechanism by

which the sodium chlorite forms chlorine dioxide is unclear.

Regardless of whether aqueous chlorine dioxide solutions are generated onsite from gaseous

chlorine dioxide, or from sodium chlorite or stabilized chlorine dioxide solutions, they are

applied manually to hard surfaces for disinfection with a sponge or mop, or as a spray.

3.2.2 Technical Maturity

Aqueous chlorine dioxide has been recognized for its disinfectant properties since the early

1900’s, and was first registered by EPA as a disinfectant and sanitizer in 1967. Sodium chloritebased cleaners are used in the food processing industry for cleaning of surfaces and of food

itself. Chlorine dioxide has extensive use in drinking water treatment, generated from sodium

chlorite and fed into the water. These applications, and the biological organisms commonly

present in these industries, are reflected in the available data regarding chlorine dioxide’s

effectiveness.

3.2.3 Applications of Aqueous Chlorine Dioxide

Wood pulp bleaching is the largest use of aqueous chlorine dioxide. Other aqueous chlorine

dioxide applications include, but are not limited to, textile bleaching, treatment of municipal

water supplies, and disinfection of food and food processing equipment. Specific examples of

such applications are discussed in Section 5.1.3 of this document.

3.2.4 Evaluation of Available Data

Various research has been conducted to test the disinfection capabilities of aqueous chlorine

dioxide. Much research has been conducted on the use of aqueous ClO2 in water distribution
33

systems. There has also been a significant amount of data generated on the effectiveness of

aqueous ClO2 as a food disinfectant. Aside from these uses, there is little experimental data

regarding aqueous chlorine dioxide surface disinfection applications. The majority of the

research conducted has been laboratory scale, aimed at determining the efficacy of ClO2 in the

destruction of pathogens and viruses deemed likely to be contaminants in those applications.

This section discusses available data concerning the effectiveness of chlorine dioxide in

destroying bacteria, fungi, and viruses. Based on the data presented, the following general

conclusions can be drawn regarding chlorine dioxide performance:

• All data pertain to biological organisms. No data are available regarding chemical

agents.

• Aqueous solutions of stabilized chlorine dioxide (slightly basic NaClO2) must be

properly activated with acid prior to use. Sodium chlorite has very few biocidal

properties by itself.

• Chlorine dioxide reacts very fast with the target organism; after 5 minutes no significant

additional reaction is typically expected.

• Chlorine dioxide is effective against certain types of bacteria, fungi, and viruses. 

However, the chemical performs better against some organisms than others. As a result,

there is uncertain predictive capability in applying results to untested organisms. 

In November 2001, EPA’s Office of Solid Waste and Emergency Response issued a crisis

exemption under Section 18 of FIFRA allowing the limited sale, distribution, and use of

products containing aqueous chlorine dioxide for surface cleaning of buildings contaminated

with spores of Bacillus anthracis. On March 28, 2002, this crisis exemption was amended to

specify the conditions for use of aqueous chlorine dioxide for decontamination. This

amendment allowed for the disinfection of hard surfaces only. Furthermore, the amendment

specified the concentration of aqueous chlorine dioxide to be 500 mg/L, to be applied at room

temperature (68 °F), with a minimum contact time of 30 minutes (EPA 2001, EPA 2002).

Further discussion of the crisis exemption for the use of aqueous ClO2 against B.

anthracis can be found on EPA’s web site at:

www.epa.gov/pesticides/factsheets/chemicals/chlorinedioxidefactsheet.htm

Disinfection/Sterilization for Bacteria and Spores

Several tests have been conducted to determine the effectiveness of commercially available

cleaners to destroy bacteria or other organisms. One test assessed the ability of various

commercially available cleaners and sanitizers to remove bacteria from various surfaces

including stainless steel and plastic (Krysinski, 1992). Material contaminated with Listeria

monocytogenes organisms were submerged in solutions for 10 minutes and then evaluated for

efficacy. Results are presented in Table 3.2-1. Stainless steel was the ‘easiest’ material to

disinfect, while a polyester/polyurethane conveyer belt was the ‘hardest.’ The log kill is modest

at these concentrations and exposure times.
34

Table 3.2-1. Deactivation of Listeria monocytogenes Using Chlorine Dioxide Solutions

Sanitizer or Cleaner Log Kill and Final Organism Count

Etched Stainless

Steel

Polyester Polyester/

Polyurethane

Chlorine dioxide (5 ppm)

sanitizer

Log kill >3.3 (Final

< 20 CFU/cm2

)

Log kill >3.2 (Final

< 20 CFU/cm2)

Log kill 0.7 (Final

9,000 CFU/cm2)

Chlorine dioxide (5 ppm) +

acidic quaternary ammonium

compound (QAC) sanitizer

Log kill >3.3 (Final

< 20 CFU/cm2

Log kill >3.2 (Final

< 20 CFU/cm2

)

Log kill 2.0 (Final

500 CFU/cm2)

Detergent/chlorine dioxide

blend of cleaner

Log kill >3.2 (Final

< 20 CFU/cm2

)

No data Log kill 1.4 (Final

2,000 CFU/cm2)

Source: Krysinski et al., 1992.

Log kill calculated as the ratio of the final counts following treatment with solution versus the final counts

of the control (no cleanser). Ten minute contact time.

Harakeh (1988) evaluated a solution of a commercially available stabilized chlorine dioxide

solution (Purogene) for the destruction of various bacteria as a function of time and pH. Bacteria

were mixed with the chlorine dioxide solution. The concentration of chlorine dioxide evaluated

was very low (0.75 mg/L) in comparison to the use levels of 500 mg/L cited in the EPA

memoranda. Nevertheless, the following conclusions and observations were identified:

• Based on tests with E. coli, pH had a significant effect on destruction. The product was

acidified to varying degrees; the greatest inactivation occurred at the lowest pH tested

(3.5). Essentially, no inactivation occurred in the pH range of 5 to 8.7. Results are

illustrated in Table 3.2-2.

• The degree of inactivation is dependent on the specific organism, as shown in Table 3.2-

3.

• The highest degree of inactivation occurred within 60 seconds. Inactivation ‘flattened

out’ between 1 and 15 minutes. For example, Table 3.2-3 illustrates that the inactivation

measured after 5 minutes is not significantly more than the inactivation measured after 15

minutes. A similar observation has been noted in other tests using sodium chloritecontaining disinfectants (Mullerat et al., 1995).

Table 3.2-2. Effect of Adding Acid to Stabilized Chlorine Dioxide Solution

pH Log Inactivation of E. coli After 5 Minutes

8.7 (initial product pH) 0.0

7 0.0

6 0.0

5 0.4

3.5 3.8

Source: Harakeh (1988). Tests conducted on stabilized chlorine dioxide product at 23 o

C. Chlorine

dioxide concentration of 0.75 mg/L.
35

Table 3.2-3. Effectiveness of Acidified Stabilized Chlorine Dioxide on Bacteria

Bacteria Log Kill After 5 Minutes Log Kill After 15 Minutes

Escherichia Coli 5.6 5.6

Pseudomonas aeruginosa 5.2 5.4

Yersinia enterocolitica 5.2 5.2

Klebsiella pneumoniae 5.0 5.0

Streptococcus pyogenes 1.9 1.9

Salmonella typhimurium 9.0 9.9

Bacillus subtilis 4.5 4.5

Source: Harakeh et al., 1988. Tests conducted on stabilized chlorine dioxide product adjusted to pH 3.5

at 23 C. Chlorine dioxide concentration of 0.75 mg/L. 

With the rising use of chlorine dioxide in water distribution systems, much research has been

conducted to verify the disinfectant abilities of chlorine dioxide as used in water treatment

facilities. For example, Tarquin and Rittmann (1993) have reported a chlorine dioxide

disinfection study conducted in El Paso, Texas, in which chlorine dioxide was tested for its

ability to reduce coliforms and total plate counts at El Paso’s 20 million gallon per day surface

water treatment plant. Chlorine dioxide was generated onsite and injected into the treatment

plant’s second set of settling tanks at a concentration of 1 mg/L. Samples were collected before

and after treatment to measure coliform bacteria and total plate counts. Table 3.2-4 presents the

results of the coliform analyses. The average coliform reduction was 83 percent.

Table 3.2-4. Coliform Reduction in Drinking Water Treated with Chlorine Dioxide

Date Coliform Count/100 ml

(before ClO2)

Coliform Count/100 ml

(after ClO2)

Percent

Reduction

7/31 860 43 95

8/07 360 12 97

8/14 620 360 42

8/21 230 0 100

8/28 385 0 100

Average 491 83 83

Source: Tarquin and Rittmann, 1993.

Chlorine dioxide administered continuously at 1 mg/L.

Similar reductions were reported for total plate counts. Plates for samples that had been

subjected to chlorine dioxide disinfection had approximately 85 percent less growth than those

samples that were not subjected to ClO2 treatment.

Tanner (1989) tested the biocidal activity of commercial disinfectants containing chlorine

dioxide. Three organisms were tested using a modified version of the Association of Official

Analytical Chemists (AOAC) use-dilution method in which a disinfecting material is combined

with a test organism in a solution. Pseudomonas aeruginosa, Staphylococcus aureus, and
36

Saccharomyces cerevisiae samples were added into the chemical solutions. Samples were drawn

after 30 seconds and 60 seconds of contact time. Chlorine dioxide was used at a concentration of

500 mg/l and diluted to lower levels. Table 3.2-5 presents the concentration required to achieve

a 5 log reduction (99.999 percent) in viable cell counts after one minute of contact time.

Table 3.2-5. Chlorine Dioxide Concentration for 5-log Reduction in Cell Count at 60

Seconds

Species

Concentration (mg/L)

ClO2 Acidified Sodium Chlorite

Pseudomonas aeruginosa 48 310

Staphylococcus aureus 93 1300

Saccharomyces cerevisiae 95 640

Tanner, 1989.

Tests conducted at 22°C. 

Ten other chemicals (including sodium hypochlorite and hydrogen peroxide) were also subjected

to the same biocidal activity tests. According to Tanner’s results, while other chemicals such as

these similarly achieved 5-log reduction against the three organisms, lower levels of chlorine

dioxide were required than for other products.

The effectiveness of chlorine dioxide for inactivating other bacteria was determined by Chauret

et al. (2001). B. subtilis spores, Clostridium sporogenes spores, and C. parvum oocysts were

evaluated. A 99 percent pure chlorine dioxide solution (generated onsite) was introduced into an

aqueous suspension of the organisms. Samples were extracted at various time intervals to

determine the remaining organism counts. Results were presented for various concentrations

and time intervals and are summarized in Table 3.2-6. A lower concentration-time value

corresponds to quicker reaction time or lower required solution concentration.

Table 3.2-6. Inactivation of Bacteria with Chlorine Dioxide

Organism Concentration@time (mg@min/L) Log inactivation

C. parvum 75 – 1,000 2.0

B. subtilis ~ 75 2.0

C. sporogenes ~ 75 2.0

Source: Chauret et al., 2001.

Results are given using the most probable number (MPN)-cell infectivity method.

Deactivation of C parvum was determined for oocysts purchased from several different suppliers; a range

is presented here.

Aqueous chlorine dioxide was tested by EPA for its sporicidal activity following the 2001

anthrax mail attacks, to support a crisis exemption under FIFRA that would allow the use of this

product against B. anthracis spores in some of the affected buildings. Tests were conducted

using the AOAC Sporicidal Activity Test (AOAC, 2000). The product tested contained either
37

500 or 1,000 mg/L ClO2, with 0.1% v/v surfactant. The sporicidal efficacy was tested using two

surfaces inoculated with 106

 B. subtilis spores: porcelain penicylinders (representing hard, nonporous surfaces) and silk suture loops (representing porous surfaces). The AOAC test does not

determine the quantitative log kill of the spores; it measures qualitatively whether or not all the

spores on the surface were killed.

The results of the testing on the porcelain penicylinders showed that, with the 500 mg/L

solution, only one of the 60 penicylinders failed to have complete kill after 10 minutes of

exposure time, and every cylinder showed complete kill after 30 minutes. By comparison, with

the silk suture loops, every one of the loops contained live spores even after 90 minutes of

exposure time to a solution containing 1,000 mg/L.

On the basis of these efficacy results, EPA issued a crisis exemption for the use of

aqueous ClO2 solutions in the B. anthracis remediation activities, with the following provisions: 

it is for use only on hard surfaces; the solution must have a ClO2 concentration of 500 mg/L; the

contact time of liquid solution on the surface must be no less than 30 minutes; and applications

should be made at room temperature (about 68 o

F, or 20 oC). Additionally, post-remediation

sampling must be performed to confirm that the remediation process – including the aqueous

ClO2 application step, and any other steps that are performed (e.g., including fumigation) – has

in fact been efficacious. Any remaining aqueous ClO2 must be removed from the treated areas

before persons without protective equipment are allowed to re-enter.

Fungicidal Activity

The effectiveness of chlorine dioxide as a fungicide was tested on post-harvest decay fungi and

filamentous fungi. Griffith et al. (1999) reported a 1994 study by Roberts and Reymond where

in vitro tests on Mucor piriformis, Botrytis cinerea, Penicillium expansum, and Cryptosporiopsis

perennans were conducted. Conidial suspensions of each pathogen were pipetted into test tubes

containing ClO2 at concentrations of 1, 3, and 5 mg/l. Samples were drawn at 30 second

intervals and the number of viable colony forming units/ml (CFU) was determined. The results

of the tests are presented in Table 3.2-7.

These experimental results indicate that deactivation is influenced by time, concentration, and

organism type. Complete deactivation (to the limits of the test) was recorded for each organism

at the highest concentrations and time identified (5 mg/L and 4 minutes); lower concentrations or

lower contact times resulted in poor results for some organisms.
38

Table 3.2-7. Mortality of Fungi After in vitro Contact with ClO2 at Various Concentrations

and Contact Times

Fungus ppm

ClO2

Percent spore mortality

30 sec. 60 sec. 120 sec. 180 sec. 240 sec.

Cryptosporiopsis

perennans

1 100 100 100 100 100

3 100 100 100 100 100

5 100 100 100 100 100

Mucor piriformis

1 85 93 99.9 99.9 100

3 100 100 100 100 100

5 100 100 100 100 100

Penicillium

expansum

1 42 77 99 99.6 99.8

3 99 99.9 100 100 100

5 100 100 100 100 100

Botrytis cinerea

1 35 49 94 98 99

3 94 99 99.7 99.9 99.9

5 99 99.5 100 100 100

Griffith et al., 1999.

Samples were diluted and placed onto malt extract agar. CFU determined after a 2-3 day incubation

period.

Virucidal Activity

In a 1981 publication by Roberts as reported by Griffith et al. (1999), the virucidal activity of

chlorine dioxide was tested for the inactivation of human infectious viruses in the effluent of

three municipal waste treatment, sewage sludge facilities in the San Francisco Bay area. 

Poliovirus I LSC was used in these experiments due to its potential as an indicator for the

Hepatitis viruses. These experiments were conducted using coliphage of Escherichia coli and

inoculum of the Poliovirus I in secondary effluents. Samples were taken at various time

intervals following 2 ppm and 5 ppm dosing of ClO2. Based on the authors’ determination that

phage survival would be indicative of the inoculum survival, coliphage survival was determined

using the Kott Method and Reverse Phage Titer Rise Reaction (RPTRR) Method. Table 3.2-8

represents the results of the experiments, as extrapolated from a graph presented in the 1981

Roberts publication. The values are indicative of the reduction in viable organism count.
39

Table 3.2-8. ClO2 Control of Poliovirus I. in Treated Sewage

ClO2 Dosage

Log Reduction of Viruses

2 minutes 5 minutes 10 minutes 30 minutes

2 ppm 1.2 2.0 2.4 2.5

5 ppm 3.2 3.7 4.0 4.7

Griffith et al., 1999

Table 3.2-8 shows that virus reduction is significantly increased with only slightly higher

chlorine dioxide levels. Griffith et al. (1999) identified that the mortality of coliform bacteria

was similar to the results in Table 3.2-8.

Biofilm Control

Mayack et al. (1984) tested the effectiveness of using chlorine dioxide for the control of biofilm. 

Table 3.2-9 presents data extrapolated from a graph in the Mayack document, showing the dry

weight and total organic carbon (TOC) reductions after chlorine dioxide use. Table 3.2-9 shows

an 82-91 percent reduction of dry weight biofilm and a 92-96 percent reduction of TOC in

biofilm at these conditions.

Table 3.2-9. ClO2 Bio-Fouling Control

Chemical

1 ppm 1 hr/day 1 ppm 15 minutes/4 times daily

Dry wt. mg/cm2 TOC mg/cm2 Dry wt. mg/cm2 TOC mg/cm2

Control 2.10 0.75 2.10 0.75

ClO2 0.38 0.06 0.18 0.03

Source: Mayack et al., 1984.

An example of the importance of biofilm control is in the control of Legionella pneumophila, the

bacteria identified in 1976 as responsible for Legionnaires’ Disease. This disease is thought to

be caused by the inhalation of bacteria contained in water mists from cooling towers and other

air handling equipment, such as a building’s ventilation system. Biofilm may be the growth

media for L. pneumophila bacteria, as well as other airborne infectious bacteria.

3.2.5 Concerns for the User

The Occupational Safety and Health Administration’s guidelines for the use and storage of ClO2

is available at www.osha-slc.gov/SLTC/healthguidelines/chlorinedioxide/recognition.html.

Chlorine dioxide is a severe respiratory and eye irritant and therefore must be handled with great

care. Protective clothing such as gloves should be worn at all times while handling liquid

chlorine dioxide. 
40

Because aqueous chlorine dioxide is essentially gaseous chlorine dioxide in solution, there exists

the safety hazard of ClO2 volitization. It is important that the ClO2 generation system be

equipped with safety features designed to prevent the concentration of chlorine dioxide from

exceeding its solubility limit (Simpson, undated).

3.2.6 Availability of the Technology for Commercial Applications

There are numerous commercial vendors for the supply of ClO2. Data for domestic and foreign

manufacturers of chlorine dioxide gas generators and liquid stabilized ClO2 are presented in

Section 5.1 of this document in the discussion of gaseous chlorine dioxide. In addition to ClO2

generators, some of these vendors also offer stabilized chlorine dioxide (SCD) products, such as

Radicate. Radicate is available in concentrated form for $50/liter (makes about 2 gallons). 

(http://www.neways.com/usa/products).

The cost of generating aqueous chlorine dioxide from chlorine dioxide gas is dependent upon a

number of factors, including the price of the generating equipment and the base chemicals used. 

The cost of generating chlorine dioxide using sodium chlorite is estimated as approximately two

to four times higher than the cost of generating chlorine dioxide from sodium chlorate (a raw

material used for extremely large scale production of chlorine dioxide). The estimated cost of

generating one metric ton of chlorine dioxide using sodium chlorate ranged from $1,100 to

$1,800 in 1992 (Kirk-Othmer, 1993).

3.2.7 Advantages and Disadvantages

Advantages of using aqueous ClO2 in remediation operations include the following:

• It has been shown to be effective in other applications, specifically water distribution

system disinfection

• It is easily applied (i.e., applied directly to the surface to be disinfected with a sponge or

mop).

• It is effective in relatively low concentrations; thereby, presenting less of an occupational

hazard during use.

• It is quick acting.

Disadvantages of using aqueous ClO2 in remediation operations include the following:

• There is a potential for bleaching of surfaces to which it is applied. Weaver-Meyers et al.

(2000) reported that a <0.02 percent (<200 ppm) aqueous chlorine dioxide solution used

to repeatedly wipe moldy books in the University of Oklahoma Libraries had a slight

bleaching effect on the spines of the books. Items wiped once showed no detrimental

effects.

• The chemical is unstable. Once prepared, the solution must be used quickly and it is

likely that certain conditions (e.g., sunlight) would accelerate its decomposition.

• Chlorine dioxide is not effective on porous surfaces. The March 2002 crisis exemption

was issued for non-porous surfaces only.
41

3.2.8 Potential Areas for Future Research

Areas for potential research specifically regarding the use of aqueous chlorine dioxide in

remediation operations include the following:

• Although the effectiveness of aqueous chlorine dioxide to decontaminate biological

agents has been widely investigated, there are no demonstrations of the use of aqueous

ClO2 against chemical contaminants (agents). 

• A data gap exists regarding the use of aqueous ClO2 against Bacillus anthracis spores. 

Currently, the susceptibility of B. anthracis spores to aqueous ClO2 is based on its

biological similarity to other species of Bacillus which have been the subject of

experiments. There is a need for systematic testing to quantify the sensitivity of B.

anthracis to ClO2 disinfection specifically, as a function of concentration and exposure

time. Likewise, the product’s efficacy against other biological threat agents could be

studied. 

• Further testing is needed to better determine the effectiveness of aqueous chlorine

dioxide on non-porous materials.

3.2.9 References for Section 3.2

AOAC, 2000. Official Methods of Analysis, 17th ed.: Method 966.04. AOAC International,

Gaithersburg, MD.

Chauret et al., 2001. Chauret, Christian P.; Radziminski, Chris Z.; Lepuil, Michael; Creason,

Robin; Andrews, Robert C. “Chlorine Dioxide Inactivation of Cryptosporidium parvum Oocysts

and Bacterial Spore Indicators.” Applied and Environmental Microbiology, 67 (7): 2993-3001

(2001).

EPA, 2001. Memorandum. FIFRA Crisis Exemption for Anthrax Incidents. From Marianne

Lamont Horinko, OSWER, to Stephen L. Johnson, OPPTS. November 9, 2001.

EPA, 2002. Memorandum. Amendment of Crisis Exemption Declaration for Use of Chlorine

Dioxide (Aqueous) to Decontaminate Structures and Other Property That have Been

Contaminated or Potentially Contaminated by Bacillus Anthracis. From Marianne Lamont

Horinko, OSWER, to Stephen L. Johnson, OPPTS. March 28, 2002.

Griffith et al., 1999. Griffith, David B.; Mainz, Eric L.; and Etherington, Roger E. Chlorine

Dioxide as an Effective Antimicrobial Pesticide for Sanitation and Disinfection. Vulcan

Chemicals, Birmingham, AL (1999). 

http://www.vul.com/vulchemicals/products/pdf/tds/sodiumch/600-601.pdf. Accessed November

2004.

Harakeh et al., 1988. Harakeh, S.; Illescas, A.; and Matin, A. “Inactivation of Bacteria by

Purogene.” Journal of Applied Bacteriology, 64: 459-463 (1988).
42

Kirk-Othmer, 1993. Encyclopedia of Chemical Technology, Fourth Edition, “Chlorine Oxygen

Acids and Salts (ClO2, HClO2),” p 977.

Krysinski et al., 1992. Krysinski, E.P.; Brown, L.J.; Marchisello, T.J. “Effect of Cleaners and

Sanitizers on Listeria monocytogenes Attached to Product Contact Surfaces.” Journal of Food

Protection, 55 (4): 246-251 (1992).

Mayack et al., 1984. Mayack, Lynn A.; Soracco, Reginald J.; Wilde, Edward W.; and Pope,

Daniel H. “Comparative Effectiveness of Chlorine and Chlorine Dioxide Biocide Regimes for

Biofouling Control.” Water Research, 18 (5): 593-599 (1984).

Mullerat et al., 1995. Mullerat, Jaime; Sheldon, Brian W.; Klapes, N. Arlene. “Inactivation of

Salmonella Species and Other Food-Borne Pathogens with Salmide, a Sodium Chlorite-Based

Oxyhalogen Disinfectant.” Journal of Food Protection, 58 (5): 535-540 (1995).

Neways, 2001. Radicate Fact Sheet. Neways, Incorporated. November 2001.

Purogene, 2003. Chlorine Dioxide - Purogene Product Description. BTC Products. 

www.btcproducts.co.za/clo_purogene.asp. Accessed November 2004.

Simpson, undated. Simpson, G.D.; Miller, R.F.; Laxton, G.D.; and Clements, W.R. A Focus on

Chlorine Dioxide: The “Ideal” Biocide. Unichem International Inc.

Tanner, 1989. Tanner, Ralph S. “Comparative Testing and Evaluation of Hard Surface

Disinfectants.” Journal of Industrial Microbiology, 4: 145-154 (1989).

Tarquin and Rittmann, 1993. Tarquin, Anthony J., and Rittmann, Douglas D. “Use of Chlorine

Dioxide for Disinfection and Taste and Odor Control.” Public Works, 124 (2): 58 (1993).

Weaver-Meyers et al., 2000. Weaver-Meyers, Pat. L.; Stolt, Wilbur A.; and Kowaleski, Barbara. 

“Controlling Mold on Library Materials with Chlorine Dioxide: An Eight-Year Case Study.”

Abbey Newsletter, 24 (4) (December 2000).
43

3.3 Aqueous Hydrogen Peroxide

3.3.1 Technology Description

Hydrogen peroxide is a strong oxidizing agent. It is commercially available in aqueous solution,

ranging in concentrations from 3 to 86 percent. Its principal uses include wood pulp and textile

bleaching, waste and wastewater treatment, and use as a chemical intermediate (Kirk-Othmer,

1995). It is also used as a household disinfectant. It has been in use in industrial and

commercial applications for over 100 years. It has been registered by EPA since 1977, as an

antimicrobial pesticide for indoor use on hard surfaces, including use in residences, medical

facilities, food establishments, and other commercial and industrial applications.

Another “peroxy” compound that is commonly used – and is often used as a supplemental

oxidizing agent in mixtures with hydrogen peroxide – is peroxyacetic acid. Peroxyacetic acid,

an organic peroxide, has been registered since 1985 as an antimicrobial pesticide for indoor use.

While hydrogen peroxide (H2O2) solution is effective as an oxidizing agent, its effectiveness

increases when dissociated into hydroxyl free radicals (i.e., OH•). For example, non-dissociated

hydrogen peroxide is not fully effective in detoxifying VX, as not all chemical bonds

contributing to the potency of this threat agent are broken by peroxide alone. However,

hydroxyl free radicals are very effective in detoxifying VX and other chemical agents (Yang,

1999). For this reason, hydrogen peroxide is often combined with other reagents to increase its

activity and effectiveness.

Many different formulations containing hydrogen peroxide have been developed and tested on

chemical and biological agents. This chapter will include discussions of formulations where

hydrogen peroxide is a principal reagent. As discussed below, hydrogen peroxide is often

combined with other ingredients which provide synergistic effects in sterilant formulations. For

example, Sandia Foam (contains hydrogen peroxide and surfactants) and Decon Green (contains

hydrogen peroxide, carbonates, molybdenum, and surfactant), each discussed elsewhere in this

report, are foam formulations with hydrogen peroxide as an active ingredient.

Liquid hydrogen peroxide is identified as being much less sporicidal than the vaporized form at

low concentrations (Carlsen and Raber, 2002). Nevertheless, data are available regarding the

effectiveness of liquid hydrogen peroxide on its ability of detoxifying both chemical and

biological agents.

In detoxifying small quantities of chemical agents or agent-contaminated surfaces, a liquid

solution containing excess reagents is frequently used (Yang, 1999). The solution contains

excess reagents that chemically convert the agent to less toxic reaction products. Hydrogen

peroxide can be used in a manner similar to other cleansing agents. The solution is applied to a

wipe (e.g., mop, sponge), spread on a surface, and allowed to stand for a period of time. While

some hydrogen peroxide residue may be left following evaporation, removal of this residue is

not necessarily required depending on the end use application of the surface. Hydrogen peroxide

solution may be considered practical for spot decontamination as well as for larger areas that are

well contained and easily accessible.
44

Additional reagents can be mixed with hydrogen peroxide to increase its effectiveness. For

example, ultraviolet light and metal catalysts (iron and copper) are effectively used for

promoting free radical formation in hydrogen peroxide to increase effectiveness. Reagents such

as organic solvents and pH adjusters are needed when detoxifying chemical agents; these

reagents increase the solubility of the chemical agent in the cleaning solution and allow for more

effective contact between the hydrogen peroxide and the toxic agent. Peroxyacetic acid and

similar organic acids – strong oxidizing agents in their own right – can be added specifically to

increase the oxidizing capability of the hydrogen peroxide in such solutions.

Solutions containing hydrogen peroxide may have a limited shelf-life. Hydrogen peroxide is

known to destabilize and decompose into water and oxygen over time (Kirk-Othmer, 1995). In

addition, the stability of a dilute solution such as one used for cleaning is typically less than that

of a concentrated material (Kopis, 2000). This is particularly the case for oxidizing chemicals. 

Therefore, it is expected to be more effective to dilute hydrogen peroxide solutions at the use site

rather than to purchase ‘ready to use’ diluted formulas.

3.3.2 Technical Maturity

There are several sterilization products on the market that contain hydrogen peroxide. These

have applications in the food and medical industries for general hard surface cleaning of

biological organisms as well as food preparation. Some of these products are discussed in

Section 3.3.4.

Additionally, there are specialized formulations available which have been developed

specifically for building or warfare decontamination. These include, among others, Sandia Foam

and Decon Green, discussed elsewhere in this report.

Other formulations have been patented, although their applications are not known. A mixture of

hydrogen peroxide and a bleach activator (e.g., tetra-acetyl ethylenediamine) forms a

peroxycarboxylic acid (in the same family as peroxyacetic acid), which is a strong oxidizer. The

solution is applied to contaminated surfaces for removal of chemical agents (Brown, 2002). As

discussed later in this section, other applications of hydrogen peroxide and peroxyacetic acid are

commercially available for biological disinfection.

3.3.3 Applications of the Technology

The greatest application for liquid hydrogen peroxide is in the bleaching of pulp and paper. Its

demand is due to its application as a more environmentally-friendly alternative to chlorine

compounds. In 1991, 49 percent of the total North American hydrogen peroxide demand was in

the pulp and paper market (Kirk-Othmer, 1995). By 2000, this use increased to 57 percent. 

Hydrogen peroxide is also used in textile bleaching, waste and wastewater treatment, and use as

a chemical intermediate (Kirk-Othmer, 1995).

Hydrogen peroxide is used as an over-the-counter biological disinfectant for indoor hard

surfaces in residential, commercial, and industrial applications.
45

3.3.4 Evaluation of Available Data

Performance data for aqueous solutions containing hydrogen peroxide – in detoxifying both

chemical and biological agents – are frequently available only from laboratory experiments, such

as liquid-phase chemical reaction data or test strip applications. Data obtained from laboratory

measurements are effective for screening or for making comparisons (Kopis, 2000). However,

there is some uncertainty in applying laboratory data towards the decontamination of surfaces in

the field; ‘field test’ data are the preferred indicator of performance. Some field data for the

hydrogen peroxide-containing Sandia foam are available for a simulated building environment,

as discussed in Section 4.1 of this document.

Based upon lab tests using the AOAC Sporicidal Activity Test, EPA has issued crisis

exemptions under FIFRA Section 18 for several aqueous products containing hydrogen peroxide,

for use in the cleaning of buildings contaminated with Bacillus anthracis (Horinko, 2002). 

Some of these products are concentrated formulations which are diluted immediately prior to use

in accordance with product instructions, while others require no dilution. Exemptions have been

issued for the following products:

• Oxonia Active, diluted to 2.1 percent hydrogen peroxide and 0.45 percent

peroxyacetic acid;

• KX-6049, diluted to 0.7 percent hydrogen peroxide and 0.45 percent peroxyacetic

acid;

• Actril Cold Sterilant and Spor-Klenz Ready to Use, each applied as an undiluted

formulation of 0.8 percent hydrogen peroxide and 0.06 percent peroxyacetic acid;

• Johnson Virex STF, applied as an undiluted formulation of 7.5 percent hydrogen

peroxide.

As shown, these formulations include hydrogen peroxide in concentrations ranging from 0.7

percent to 7.5 percent, and peroxyacetic acid in concentrations ranging from 0.06 percent to 0.45

percent. Peroxyacetic acid (also known as peracetic acid, CH3COOOH), like hydrogen peroxide,

is an oxidizing agent. 

The crisis exemption issued for each of these aqueous peroxide products specifies the conditions

under which they must be applied for treatment of B. anthracis. All of the products must be

utilized only on hard surfaces; must be applied at room temperature (68 o

F, or 20 oC); and must

have a contact time of at least 10 to 20 minutes, depending upon the specific product. The extent

of product dilution prior to use is also specified. Further information is available on EPA’s web

site,

 www.epa.gov/pesticides/factsheets/chemicals/hydrogenperoxide_peroxyaceticacid_factsheet.ht

m

Performance Towards Chemical Agents

In some instances, chemical agents react to form toxic end products, depending on the reactants

used (Wagner and Yang, 2002). For example, for VX, perhydrolysis (reaction of OOH–, formed

from hydrogen peroxide) minimizes or avoids the generation of a toxic byproduct – S-[2-

(diisopropylamino)ethyl] methlylphosphonothioic acid, called EA 2192 – which is generated
46

from simple hydrolysis (reaction of OH–). As another example, HD can be hydrolyzed to

nontoxic thiodiglycol by simple hydrolysis (although the nucleophilic substitution is slow).

HD can be rapidly oxidized to form two reaction products, a sulfone (which has severe irritating

vesicant properties) and sulfoxide (which does not). Hypochlorites and peroxyacids rapidly

oxidize HD, but the reaction is non-selective, producing both sulfoxide and sulfone. Hydrogen

peroxide, a milder oxidant, selectively yields the nonvesicant sulfoxide, although at a less rapid

reaction rate. The rate with hydrogen peroxide can be increased with the addition of peroxide

activators (such as bicarbonate and molybdate), discussed further below.

The U.S. Army Edgewood Chemical Biological Center (ECBC) has examined the detoxification

of chemical agents (including VX, GB, and HD) with hydrogen peroxide (Wagner and Yang,

2002). Liquid-phase reactions of these chemical agents with hydrogen peroxide-containing

reagents were conducted in test tube experiments. The reagents were mixtures of hydrogen

peroxide, activators such as sodium bicarbonate (to promote dissociation of the hydrogen

peroxide into more chemically-active components), and co-solvents such as t-butanol (to

increase the solubility of the chemical agent). Hydrogen peroxide concentrations ranged from

11 percent to 30 percent. Reaction speed was recorded as half-life, which is the time required

for half of the chemical agent to react (a lower half-life corresponds to higher reaction speed). 

On this basis, 10 half-lives would be required to achieve a 3-log reduction, and 20 half-lives to

achieve a 6-log reduction (if reaction time is independent of the chemical agent concentration). 

The results observed by ECBC are presented in Table 3.3-1.

Table 3.3-1. Reaction of Hydrogen Peroxide-Containing Solutions with Chemical Agents

Reagents Present (combination of peroxide,

activator, and alcohol)

Observed Half-Life

VX GB HD

15% Hydrogen peroxide and t-butanol >> 16 hr 29 days 42 min

15% Hydrogen peroxide, 0.037M sodium

bicarbonate solution, and t-butanol

120 min <1 min 20 min

22-26% Hydrogen peroxide, 0.1M sodium

bicarbonate solution, and t-butanol

11 min <1 min 2.1 min

22-26% Hydrogen peroxide, 0.1M sodium

bicarbonate solution, and either ethanol, isopropanol,

or polypropylene glycol

No data No data 1.8 -

1.9 min

30% Hydrogen peroxide, 0.33M sodium bicarbonate

solution, and t-butanol

56 sec No data No

data

11% Hydrogen peroxide, urea, 0.75M sodium

bicarbonate solution, and t-butanol

7.5 min <1 min 1.6 min

28% Hydrogen peroxide, 0.2M potassium

bicarbonate, and isopropanol/ Triton X-100 polyether

alcohol

2.6 min No data 2.1 min
Reagents Present (combination of peroxide,

activator, and alcohol)

Observed Half-Life

VX GB HD

47

28% Hydrogen peroxide, 0.1M potassium

bicarbonate/ 0.1M potassium carbonate, and

isopropanol/ Triton X-100 polyether alcohol

<1 min 2.4 min at room

temperature; 189

min at -30 o

C

No

data

28% Hydrogen peroxide, 0.1M potassium

bicarbonate/ 0.1M potassium carbonate/ 0.01M

potassium permanganate, and isopropanol/ Triton X100 polyether alcohol

<1 min <<30 sec at

room

temperature; 5.7

min at -30 oC

No

data

Source: Wagner and Yang, 2002.

Earlier results from ECBC examined pH variations and the use of catalysts in chemical agent

destruction with hydrogen peroxide. Results regarding the performance as a function of pH are

shown in Table 3.3-2. Results regarding the performance of different catalysts are shown in

Table 3.3-3.

Table 3.3-2. Effect of pH on VX Detoxification Using Hydrogen Peroxide

Reagent pH Conditions Result of VX Detoxification

0.5M Solution of

peroxycarbonate (sodium

carbonate and hydrogen

peroxide)

Slightly basic ‘Complete’ hydrolysis of VX

in less than two minutes

14% Hydrogen peroxide Slightly acidic (initial pH 4) Initial rapid reaction; reaction

stopped with 47% VX

remaining

Hydrogen peroxide and up to

6M of a strong acid such as

hydrochloric acid

Strongly acidic Results in dissolution of VX

and subsequent detoxification

to an unspecified degree

Source: Yang, 1999.
48

Table 3.3-3. Effectiveness of Hydrogen Peroxide and Catalysts on Chemical Agents

Chemical

Agent

Formulation Catalyst Added Result

HD in solution 1% hydrogen peroxide in

50-50% (volume) water/

N-cyclohexyl-2-

pyrrolidinone (at 21 o

C).

None Half-life of 6 hours

HD in solution 1 M hydrogen peroxide

(about 3 percent) in

acetonitrile (at 20 o

C).

0.01 M vanadium

catalyst,

VO[(CH3CO)2CH 2]2

Complete

conversion < 2

minutes

VX in solution “Not effective”

VX or HD Hydrogen peroxide in

unspecified solutions

Iron-containing

catalysts

“Not effective”

Source: Yang et al., 1992.

Based on the data in Tables 3.3-1 to 3.3-3 and additional discussions in the source documents

(Yang, 1999; Wagner and Yang, 2002; Yang et al., 1992), the following conclusions are

available regarding the effectiveness of hydrogen peroxide on chemical agents:

• Most data are available for the agent in solutions or suspensions and therefore there is

some uncertainty in extrapolating the results to a surface application.

• Co-solvents (water soluble organic solvents) are needed to increase the contact between

hydrogen peroxide and the chemical agent. Chemical agents are typically insoluble in

water.

• Hydrogen peroxide alone, or hydrogen peroxide with a solvent, exhibits poor

performance for the GX, HD, and VX agents.

• Performance is significantly improved with the addition of a carbonate activator and/ or

certain catalysts. Various combinations resulted in a half-life of less than one or two

minutes. Assuming that reaction time is independent of agent concentration, a 3-log

reduction in concentration is achieved in 20 minutes and a 6-log reduction in

concentration is achieved in 40 minutes for formulations in Tables 3.3-1 to 3.3-3 with a

half-life of two minutes or less.

• Activators increase the effectiveness of hydrogen peroxide. The reaction speed increases

for all three agents (VX, GB, and HD) as the activator concentration increases.

• Chemical agents react differently to activators. GB is deactivated rapidly in all

conditions where an activator is present, and therefore is somewhat ‘easier’ to treat. In

the case of VX, the fastest reaction results from the use of a mixture of potassium

bicarbonate and potassium carbonate. For HD, the fastest reaction results from the use of

a mixture of potassium bicarbonate, potassium carbonate, and potassium molybdate.

• None of the chemical agents were tested with a commercially available hydrogen

peroxide/peracetic acid product (or similar) such as those identified in the EPA

exemption. Due to their low solubility in water, however, significant destruction of these

agents in such products would not be expected.
49

Performance Towards Biological Agents

Whereas chemical agent detoxification data are available solely from the ECBC, data regarding

the effectiveness of hydrogen peroxide towards biological agents are available from many

different sources.

One study evaluated the effectiveness of hydrogen peroxide in killing bacteria from sponges

(Ikawa and Rossen, 1999). Results from this study potentially can be used to assess the

penetrating ability of hydrogen peroxide, as well as the effectiveness of ‘off the shelf’ hydrogen

peroxide. In this study, bacteria-containing sponges were soaked for five minutes in a

commercial three percent hydrogen peroxide solution. Testing was conducted on common

household scrubber sponges. Results are presented in Table 3.3-4. The results show that a three

percent hydrogen peroxide solution has limited effectiveness in destroying certain types of

bacteria present within the sponges. As shown, some bacteria are treated extremely effectively

while for others treatment is ineffective. In addition, hydrogen peroxide appears to have the

ability to penetrate the porous texture of a sponge.

Table 3.3-4. Reduction of Bacteria in Sponges Following Hydrogen Peroxide Treatment

Sponge Type Bacterial

Reduction

Post-treatment

Bacteria Count

Bacteria Type

Laboratoryinoculated

household

scrubber sponge

99.998% Not detected

(<10 CFU/

sponge)

Combination of Escherichia coli,

Salmonella choleraesuis, Pseudomonas

aeruginosa, Staphyloccus aureus, and

Shewanella putrefaciens

Consumer-used

household

scrubber sponge

56.2% 3.2x106

 CFU/

sponge

Bacteria resultant from day-to-day

kitchen use; species not determined

Tests conducted by soaking sponge for five minutes in a three percent hydrogen peroxide solution.

Source: Ikawa and Rossen, 1999.

The activity of a hydrogen peroxide formulation was tested by spraying solution onto glass

slides inoculated with various organisms and allowing the material to sit for two hours (Elhaik

and De Nicola, 2001). The relatively weak formulation consisted of six different individual

components, as follows: (1) hydrogen peroxide, (2) organic acid, (3) silver salt, (4) phosphoric

acid, (5) a surfactant, and (6) a corrosion inhibitor. The first three components, in combination,

provide disinfection properties. The phosphoric acid acts as a stabilizer. Results are shown in

Table 3.3-5. The tests showed that the more concentrated solutions displayed a higher kill rate

than the less concentrated solutions. Other tests showed that the performance of the solution was

lower when either the organic acid or the silver salt was removed; hydrogen peroxide

performance improved with the addition of these components.
50

Table 3.3-5. Performance of Hydrogen Peroxide-Containing Formulation 

Sprayed Onto Glass Slides

Strain

Log Kill Rate

Solutions consisting of:

1.6 - 4% Hydrogen peroxide

1 - 2.8% acetic acid/peracetic

acid

16-25 ppm silver

16-25 ppm phosphoric acid

80-200 ppm surfactant

64-160 ppm corrosion inhibitor

Solutions consisting of:

0.8% Hydrogen peroxide

0.5% acetic acid/peracetic acid

2-10 ppm silver

4-10 ppm phosphoric acid

20-40 ppm Surfactant

20-32 ppm corrosion inhibitor

Staphylococcus aureus 6.3 5.2-5.3

Pseudomonas

aeruginosa

6.2 5.1-5.2

Enterococcus faecium 5.2 5.1-5.2

Mycobacterium

smegmatis

5.1 5.1-5.2

Candida albicans 5.3 4.2-5.0

Penicillium verrucosum 5.1-5.2 3.8-4.1

Bacillus subtilis 3.6 3.6

Source: Elhaik and De Nicola, 2001.

Note: 1% = 10,000 ppm

Solution was allowed to set on glass slides for two hours following spray application.

Conditions: 80% humidity, 24 o

C.

A synopsis of available data regarding the effectiveness of hydrogen peroxide on B. anthracis is

available (Spotts-Whitney et al., 2003). A 100 percent kill rate was reported for a 0.88 M (about

3 percent) hydrogen peroxide solution at pH of 4.3 to 5. Results of 100 percent kill were

reported after 3 hours for a spore suspension of 106

 CFU/mL, and 100 percent kill was reported

after 6 hours for a stainless steel carrier coated with a spore suspension (initial challenge dose

not specified).

Another study examined the effectiveness of mixtures of hydrogen peroxide and other additives

towards killing viruses and bacteria (Sagripanti, 1992). These results were conducted in

suspensions. The results showed that hydrogen peroxide alone was relatively ineffective at low

concentrations, but when combined with copper there was a far greater degree of virus

inactivation. Results are shown in Table 3.3-6.
51

Table 3.3-6. Effectiveness of Hydrogen Peroxide on Biological Agents

Biological

Agent

Hydrogen Peroxide

Concentration

Other Additives Result

Junin virus 110 mg/L (about

0.01%)

None 50% reduction

170 mg/L (about

0.02%)

10 mg/L copper 3.5 log reduction

after 30 minutes

B. subtilis 5% 0.2% copper 3-log reduction after

35 minutes; >5-log

reduction after 60

minutes

Results at 21 oC.

Source: Sagripanti, 1992.

In contrast to the above apparent effectiveness of copper, one study examined the effectiveness

of hydrogen peroxide on B. globigii spores (Cross et al., 2003). A spore suspension was exposed

to a solution of 0.1 M hydrogen peroxide (about 0.3 percent) and 0.6 M copper (II) for 30

minutes. The tests were repeated with the addition of 0.1 M ascorbic acid. All tests using the

above mix of reagents resulted in only a 1-log kill (i.e., ten percent of the spores survived). The

reagents selected for these tests were intended to result in the formation of hydroxyl free

radicals.

Based on the above data regarding the performance of hydrogen peroxide towards biological

organisms, the following conclusions are available:

• Most data are available for the agent in solutions or suspensions and therefore there is

some uncertainty in extrapolating the results to a surface application.

• A solution of 3 percent hydrogen peroxide is sufficiently effective towards destroying B.

anthracis and several types of bacteria. For another type of virus (Junin virus), results

are inconclusive because a low hydrogen peroxide concentration (0.01 percent) resulted

in low kill rate (50 percent); data for higher concentrations are not available.

• Very effective destruction (5 to 6 logs after 2 hours) for various strains was found for

peracetic acid/hydrogen peroxide formulations when combined with other reagents,

including silver. EPA evaluated confidential testing results of peracetic acid/hydrogen

peroxide formulations on hard nonporous surfaces and issued its product-specific crisis

exemptions, in part, on the basis of these results.

• Metals (in particular copper and iron) have mixed results in increasing the effectiveness

of hydrogen peroxide. These metals have well documented effects in transforming

hydrogen peroxide into free radicals and therefore in theory would be expected to

increase performance. It is possible that the degree of this increased performance

depends on the particular organism.
52

3.3.5 Concerns for the User

Hydrogen peroxide is a strong oxidizer; therefore, precautions for skin, inhalation, and eye

protection are needed when handling products containing this chemical in any concentration. 

Most formulations for use are relatively dilute and present less of a risk than more concentrated

solutions, such as those used for vapor hydrogen peroxide. Some other precautions regarding

vapor hydrogen peroxide, as discussed in Section 5.3.5, are also applicable to liquid hydrogen

peroxide.

Significant additional shipping fees are required when purchasing any product containing

concentrated hydrogen peroxide. Hydrogen peroxide in concentrations of 8 percent or more

requires hazardous material shipping. Solutions containing hydrogen peroxide at concentrations

less than this may or may not require hazardous material shipping designation depending on the

other ingredients present.

3.3.6 Availability of the Technology for Commercial Applications

Many different hydrogen peroxide-containing products are on the market. In addition, hydrogen

peroxide alone can be purchased. The availability and cost of several of these alternatives are as

follows:

• Actril Cold Sterilant (supplied by Minntech). This formulation contains 0.8 percent

hydrogen peroxide and 0.06 percent peracetic acid.. Based on 2003 correspondence with

the supplier, the cost for a case of four 1-gallon containers is $70.70 (with test strips

included) or $51.25 (for the formulation only).

• Concentrated hydrogen peroxide (many suppliers possible). This is technical grade 35

percent hydrogen peroxide. Based on a supplier’s 2003 web page (Clyde Co-Op), the

cost for a 1-gallon container is $49.38. (As discussed in Section 5.3, this is the

concentration used for vapor hydrogen peroxide applications.)

Several of the formulations described in Section 3.3.4 have uncertain availability. For example,

combinations of hydrogen peroxide, carbonates, and metals were prepared using the individual

chemicals. While these chemicals are readily available, it is inconvenient and probably

impractical to prepare such formulations at a use site.

3.3.7 Advantages and Disadvantages

A principal advantage for hydrogen peroxide is that it breaks down into environmentally benignproducts --- water and oxygen. As a liquid solution, it is easy to apply (e.g., sponge, mop,

spray). Another advantage cited for liquid hydrogen peroxide is that it does not freeze under

most conditions. However, at low temperatures, the reaction time is slowed considerably

(Wagner and Yang, 2002).

Hydrogen peroxide is a an oxidant; therefore, it is expected to detrimentally affect color in

textiles, carpet, etc. In addition, its effectiveness towards porous materials, such as textiles and

carpets, has not been demonstrated.
53

Like other liquid phase decontaminants and sterilants, the surface must remain wet for the active

ingredient to be efficacious against the target organism. In addition, for most products, the

surface to be treated should be pre-cleaned. The correct concentration, contact time, and

temperature for application of each product are determined by the results of the efficacy testing

for that product.

The effectiveness of hydrogen peroxide in destroying G agents, such as GB, is identified as

about equal to the performance of an unmodified base solution (e.g., of NaOH), having a pH just

above 7. For the G agents, there is little advantage to using hydrogen peroxide. However, for

VX, the use of base solutions result in the formation of a toxic byproduct, which does not result

from the use of hydrogen peroxide (Wagner and Yang, 2002).

3.3.8 Potential Areas for Future Research

Additional data are desirable in several areas. More data regarding the effectiveness of hydrogen

peroxide and/or peracetic acid is desirable, particularly with regard to porous and nonporous

surfaces. There may be difficulties in the practical building decontamination application of

some of the peroxide formulations that have been found to be effective in the lab. Therefore,

formulations or on-site recipes may need further development.

3.3.9 References for Section 3.3

Brown, 2002. Brown, Jerry S. Chemical and Biological Warfare Decontaminating Solution

Using Bleach Activators. U.S. Patent No. 6,369,288. April 9, 2002.

Carlsen and Raber, 2002. Carlsen, Tina; and Raber, Ellen. “The Use of Vaporous Hydrogen

Peroxide for Building Decontamination.” CBNP 2002 Summer Meeting Abstracts, pp 43-44. 

July 30, 2002.

Cross et al., 2003. Cross, J.B.; Currier, R.P.; Torraco, D.J.; Vanderberg, L.A.; Wagner, G.L.;

and Gladen, P.D. “Killing of Bacillus Spores by Aqueous Dissolved Oxygen, Ascorbic Acid,

and Copper Ions.” Applied and Environmental Microbiology, 69 (4): 2245-2252 (2003).

Elhaik and De Nicola, 2001. Elhaik, Alain; and De Nicola, Raphaël Alex. Aqueous

Composition Containing H2O2, Acids and Ag, Preparation Method Therefor and Use Thereof for

Disinfection, Hygiene and/or Pollution Control. U.S. Patent No. 6,277,414. August 21, 2001.

Horinko, M.L. 2002. Memoranda to Stephen L. Johnson, regarding FIFRA Crisis Exemption

for Anthrax Incidents. February 14, 2002; March 28, 2002; June 25, 2002.

Ikawa and Rossen, 1999. Ikawa, Judy Y.; and Rossen, Jonathan S. “Reducing Bacteria in

Household Sponges.” Environmental Health, July/August 1999, pp 18-22.

Kopis, 2000. Kopis, E.M. “Surface Decontamination: Selection, Control, and Validation of

Cleanroom Sanitizing Agents.” Pharma + Food International, 2000, pp 66-69.
54

Kirk-Othmer, 1995. Encyclopedia of Chemical Technology, Fourth Edition, Volume 13. 

“Hydrogen Peroxide”.

Sagripanti, 1992. Sagripanti, Jose-Luis. “Metal-Based Formulations with High Microbicidal

Activity.” Applied and Environmental Microbiology, 58 (9): 3157-3162 (1992).

Spotts-Whitney et al., 2003. Spotts-Whitney, Ellen A.; Beatty, Mark E.; Taylor Jr., Thomas H.;

Weyant, Robbin; Sobel, Jeremy; Arduino, Matthew J.; Ashford, David A. “Inactivation of

Bacillus anthracis Spores.” Emerging Infectious Diseases, 9 (6). 2003.

Wagner and Yang, 2002. Wagner, George W.; and Yang, Yu-Chu. “Rapid Nucleophilic/

Oxidative Decontamination of Chemical Warfare Agents.” Industrial Engineering and

Chemistry Research, 41: 1925-1928 (2002).

Yang, 1999. Yang, Yu-Chu. “Chemical Detoxification of Nerve Agent VX.” Accounts of

Chemical Research, 32: 109-115 (1999).

Yang et al., 1992. Yang, Yu-Chu; Baker, James A.; Ward, J. Richard. “Decontamination of

Chemical Warfare Agents.” Chemical Reviews, 92: 1729-1743 (1992).
55

3.4 TechXtract® Contaminant Extraction Technology

TechXtract is a decontamination technology that chemically extracts hazardous substances from

solid materials such as concrete, brick, steel, and wood. It is a proprietary process with a

proprietary set of chemical mixtures used for treatment. TechXtract is designed to remove

organics, metals, or radionuclides from the surface and subsurface of porous and nonporous solid

materials in a series of application, penetration, and extraction steps. 

3.4.1 Description of the Technology Alternative

Environmental Extraction Technologies, Inc. (EET) is a division of Active Environmental

Technologies, Inc. (ACT). EET calls their TechXtract a "contaminant extraction technology". 

The technology can be used for treating floors, walls, ceilings, and equipment. The mixtures

may include emulsifiers, buffered organic and inorganic acids, and hydrotropic, electrolyte,

flotation, wetting, and sequestering agents that extract the contaminants and bring them to the

surface. The chemical mixtures are applied sequentially, in successive cycles. Each treatment

cycle includes application, penetration, and extraction. Wet vacuuming is used to remove the

solutions from the treated substrate.

Effective decontamination of a porous surface is one of the more challenging aspects of building

decontamination. TechXtract’s effectiveness in decontamination of porous surfaces is, in part,

because it uses wetting agents to increase permeation into pores, and because it uses wet

vacuuming to get treatment solutions back out of pores.

Although TechXtract is a proprietary process, EET describes the types of chemicals used in their

process generically in their advertising literature and on their Internet web site. More detail on

specific chemicals used in TechXtract formulations is provided in their patents (Borah, 1995,

1996, 1998; Tyerech, 1998).

How TechXtract Is Used

EET uses and sells chemical formulations called TechXtract 100, 200, and 300. TechXtract 100

is used in one type of treatment cycle. It contains macro- and micro-emulsifiers, as well as

electrolyte, flotation, wetting, and sequestering agents. It is applied to the surface being treated

as a fine mist, then worked into the surface using an abrasive pad. Then the TechXtract is

allowed at least 45 minutes to penetrate into the subsurface. A rinse formula, of ten percent

TechXtract 300 mixed with water, is sprayed onto the surface being treated. Then the treatment

chemicals and contaminants are removed using a wet vacuum.

The other type of treatment cycle uses TechXtract 200 and 300, and often follows a TechXtract

100 cycle. TechXtract 300 is applied first, and worked into the surface using an abrasive pad. 

Then TechXtract 200 is immediately applied using the same procedure. EET claims that

TechXtract 200 and 300 work together synergistically. They contain buffered organic and

inorganic acids, sequestering agents, wetting agents, and hydrotropic chemicals. 
56

The number of TechXtract 100 and 300/200 cycles used for a given decontamination situation

will depend on the contamination levels, the difficulty of removal of the contaminant from the

matrix, and the depth of the contamination.

TechXtract formulations are applied with abrasive scrubbing, such as with a scrub brush,

abrasive pad, or electric floor polisher. This helps remove surface contamination, allowing

access by the formulations to the subsurface, and mechanically enhancing penetration.

TechXtract usually solubilizes and extracts, rather than destroying the target compound. 

Therefore, the liquid wastes contain the extracted contaminants, and must be discarded. In some

cases, oxidizing agents are used in the formulations, in which case oxidation products are

produced as secondary waste. Small amounts of the TechXtract chemicals are likely to remain

in the treated matrix, especially if the matrix is porous. EET says that none of the TechXtract

constituents, when spent, will be characterized as hazardous wastes under the Resource

Conservation and Recovery Act (RCRA).

By design, a very small amount of the substrate is leached or removed by TechXtract to facilitate

release of contaminants. This may result in an unacceptable effect to the surfaces of expensive

or sensitive materials.

Functions of the TechXtract Formulation Components

The chemical warfare agents and industrial chemicals most likely to be used in a terrorist

scenario would probably be organic chemicals. Therefore, the functions of the treatment

chemicals used in TechXtract formulations are discussed here in the context of remediating

buildings contaminated with hazardous organics.

Emulsifiers are surface-active chemicals that, in TechXtract applications, stabilize suspensions

of organics (having low aqueous solubility) in aqueous matrices. They perform like detergents. 

The emulsifiers mentioned by EET in their patent for removal of contaminants from surfaces

were quaternary amines.

Flotation agents are another type of surface-active chemical, that will cause solid metalcontaining particles to adhere to air bubbles and float to the surface of liquids. They would be

most useful for heavy metal or radionuclide removal from a contaminated matrix. They would

also help to open up an inorganic matrix (such as concrete, brick, or stone) to allow organics

extraction. Flotation agents are widely used in the mining industry, for separation of metalcontaining ore particles from the low metal content ore tailings.

Wetting agents are another type of surface-active chemicals used in TechXtract formulations. 

They decrease the surface tension of aqueous solutions, enhancing their ability to penetrate into

small pores and crevices. This would be expected to greatly increase the decontamination

effectiveness of TechXtract formulations for porous matrices such as concrete and wood. 

Wetting agents are used in agriculture, where they are called soil penetrants, because they

enhance the permeation of beneficial chemicals (nutrients and pesticides) through the soil matrix

to the plants’ roots, where they can be most effective.
57

Sequestering agents are chemicals that form complexes or chelates with metals, enhancing the

extractability of the metal by aqueous formulations. When removing organic contaminants from

metal surfaces, and from the boundaries between metal grains in a metal object, sequestering

agents will dissolve small amounts of the metal surface, releasing the organics to the extractant

formulation and enhancing their removal. Sequestering agents are widely used for cleaning

metal surfaces, and for solubilizing nutrient metals for plants in the horticultural and agricultural

industries. TechXtract patents mention a variety of sequestering agents, including nitrilotriacetic

acid, hydroxyethylene diamine tetraacetic acid, and ethylenediamine tetraacetic acid (EDTA).

Buffered organic and inorganic acids have at least three purposes. They release contaminants

from metal surfaces by dissolving some of the metal, analogous to sequestering agents. 

Ammonium bifluoride, which releases hydrofluoric acid in aqueous solution, is used

commercially to remove vitreous enamel from metal surfaces. Its ability to solubilize silica and

silicate matrices is probably why it is used in TechXtract formulations. Stone, brick, and glass

are silica and silicate types of building materials whose decontamination would be enhanced by

ammonium bifluoride to dissolve their surface and open the matrix. Some polyfunctional

organic acids used in TechXtract, like oxalic acid and citric acid, are also sequestrants. (Oxalic

acid is used commercially to remove rust stains.) Organic acids with aliphatic hydrocarbon

chains will also act as co-solvents for organic contaminants and for organic emulsions of

contaminants. (See hydrotropic chemicals.) The buffering of the acids helps control the amount

of metal that is removed from a surface, so that damage to the surface is minimal or negligible.

Hydrotropic chemicals (also known as co-solvents) increase the solubility of other chemicals in

water-based solutions. They typically have both hydrophilic and hydrophobic components in the

same molecule, similar to surfactants, but they form solutions rather than suspensions. Ethylene

glycol monobutyl ether and glycerine are examples of hydrotropic chemicals used in TechXtract

formulations.

Electrolytes may be contained in TechXtract formulations. In its patents, EET makes it clear

that de-ionized or distilled water is used in its formulations, to minimize ions in solution that

would decrease the effectiveness of the formulations. Tap water tends to contain variable levels

of cations, such as the divalent cations magnesium and calcium, which use up the sequestrants.

Salts in solution can decrease the effectiveness of the nonionic surfactants in emulsifying target

organics. In some cases, however, EET uses monovalent cations (such as Na+) to disrupt the

links between matrix divalent cations (such as Ca++ and Mg++) and contaminants, to separate

contaminants from surface charged matrices such as concrete or clays (SAIC, 2003).

It is apparent that TechXtract formulations draw on a wide variety of surface cleaning, and

contaminant solubilization and mobilization technologies that have been individually proven in

other industries. Their integration into a single decontamination technology, or array of

decontamination formulation variants, by EET is one of the innovative aspects of TechXtract. 

The ability of TechXtract formulations to penetrate into porous surfaces by using wetting agents,

and the wet vacuuming to get treatment solutions back out of pores, are the other most

significant innovations of this technology. 
58

3.4.2 Technical Maturity 

TechXtract is an array of technologies that have been integrated into commercial

decontamination service. Some elements of the technology, such as the use of surfactants in

aqueous solutions to remove organic contaminants, and the use of chelating agents to remove

heavy metal contaminants, are mature technologies, used widely in industry for decontamination

applications. Other elements of TechXtract, such as the use of Fenton’s reagent, wetting agents,

ammonium bifluoride, monovalent cations, and flotation agents for decontamination applications

are less mature elements of decontamination technology. These technologies are mature for

other industrial applications, but their use in building decontamination is innovative and less

mature.

None of the decontamination projects performed with TechXtract have involved chemical

warfare agents (CWAs). Because most applications of the technology have been removals rather

than in-place chemical destructions, and many of the successful applications have been the

removal of difficult hydrophobic organics, there is little question that TechXtract will be able to

remove VX, HD, and the G-agents from a variety of building material substrates. The CWAs

would then have to be treated and disposed as hazardous waste. 

Some of the acidic ingredients used in TechXtract formulations might hydrolyze CWAs in place. 

If the Fenton’s reagent version of TechXtract were applied to CWAs, which uses hydroxyl

radicals and ozone to oxidize contaminants, it is likely that the CWAs would be, at least

partially, destroyed in place (converted to much less toxic products). These applications have

not been tested; there is no assurance of their success (See section 3.4.8).

The simplicity of the application and removal of TechXtract formulations to and from a substrate

to be decontaminated, in multiple stages depending on the difficulty of the task, makes the

technology readily scalable to large and small tasks. The cost per unit area of the

decontamination task will be higher for small areas than for large areas, because the cost for

mobilization is a relatively fixed cost. For tasks over about 5000 ft2

, the material and labor costs,

which are proportional to the size of the cleanup, will be the dominant costs (see section 3.4.6). 

3.4.3 Applications of the Technology 

The TechXtract array of decontamination technologies is fully commercialized. It is available as

a service performed on site by EET, or as a commercially available set of products, with training

services available as well (see section 3.4.6).

EET claims to have used TechXtract decontamination in over four hundred applications, with a

99 percent success rate (EET, 2004). It has been applied to removal of organics from concrete

and granite floors and large metal equipment, which are target applications relevant to terrorist

contamination of buildings.
59

TechXtract was tested by the Hanford Site C Reactor Technology Demonstration Group, under

the auspices of the U.S. Department of Energy’s (DOE’s) Federal Energy Technology Center,

for the removal of radionuclide contamination from the surface of lead bricks (DOE, 1998).

3.4.4 Evaluation of Available Data 

The following paragraphs describe two decontamination projects performed with the TechXtract

technologies that illustrate its applicability to building cleanups.

Polychlorinated Biphenyl (PCB) Transformer Oil Extraction from Concrete Floor in Building

The TechXtract technology was tested under the EPA’s Superfund Innovative Technology

Evaluation (SITE) Program in 1997 for removal of PCBs on concrete (U.S. Navy, 1997; EPA,

1998). The following paragraphs describe the test.

A field demonstration of TechXtract was performed under the SITE Program, in cooperation

with the U.S. Navy’s Pacific Division of the Naval Facilities Engineering Command (PACDIV)

and the Pearl Harbor Public Works Center (PWC), at the Pearl Harbor Naval Complex on Oahu,

Hawaii. A concrete floor, 124 square feet in area, was contaminated with PCBs and oils,

including a 14 square foot area of high PCB concentrations and visible staining. The

demonstration was performed during February and March, 1997.

Pretreatment wipe samples, of 100 cm2

 areas of the surface, showed PCB levels of 10,000 to

32,000 μg/100 cm2

. Pretreatment concrete core samples showed up to 3.5 percent subsurface

PCBs, including as high as 2.5 percent at 2 to 4 inches below the concrete surface. 

PWC staff performed the decontamination, after having been trained by EET staff. Twenty

TechXtract 100 and twelve TechXtract 300/200 cycles were applied to the PCB contaminated

concrete floor.

The significant ability of TechXtract to remove surface PCBs is indicated by the wipe sample

data in Table 3.4-1. For the three most contaminated surface locations (where PCBs were

10,000 μg/100 cm2

 or greater), the contaminant removal efficiency was 99.5 to 99.8 percent. For

the other thirteen surface locations with PCB levels below 1000 μg/100 cm2

, the removal

efficiency was between 81 and 99.7 percent.

The subsurface decontamination effectiveness of TechXtract was variable, and the data show

that the technology is not as effective as it is for surface contamination. Table 3.4-2 shows data

indicating significant PCB removal at only one of five coring locations (C3). The other four sets

of coring results (locations C1, C2, C4, and C5) indicate that subsurface contamination was

unchanged or increased during the decontamination process.
60

Table 3.4-1. Surface PCB Removal Based on Wipe Samples

Location Total PCBs (ug/100 cm2) Change Pre-Treatment Post-Treatment

W1 11 1.6 - 85%

W2 32,000 79 - 99.8%

W3 140 11 - 92%

W4 39 1.5 - 96%

W5 28 5.4 - 81%

W6 41 1.5 - 96%

W7 10,000 48 - 99.5%

W8 940 6.4 - 99.3%

W9 47 1.3 - 97%

W10 17 2.3 - 86%

W11 32 3.9 - 88%

W12 40 <1.0 - 98%

W13 35 <1.0 - 97%

W14 11,000 34 - 99.7%

W15 290 <1.0 - 99.7%

W16 85 12 - 86%

Table 3.4-2. PCB Removal at Depth Based on Corings

Location Depth Below

Surface (inches)

Total PCBs (ug/g)

 Pre-Treatment Post-Treatment

Change

C1 0 - 1

1 - 2

2 - 4

32,000

22,000

15,000

30,000

19,000

16,000

-6%

-14%

+6%

C2 0 - 1

1 - 2

2 - 4

35,000

29,000

25,000

27,000

30,000

21,000

-23%

+3%

-16%

C3 0 - 1

1 - 2

2 - 4

14,000

33,000

24,000

330

39

120

-98%

-99.9%

-99.5%

C4 0 - 1

1 - 2

2 - 4

3,400

12,000

13,000

29,000

17,000

13,000

+850%

+140%

0%

C5 0 - 1

1 - 2

2 - 4

4.80

0.11

0.48

26

9.1

6.2

540%

830%

130%
61

Figure 3.4-1. Locations of

Wipe and Coring Samples

Figure 3.4-1 shows where the wipe and coring samples were

collected. All of the coring samples were collected in or near

the oil stained area, which is probably where the

contamination was heaviest. Although EET did not analyze

for oils other than PCBs, it is quite possible that the concrete

was more organics saturated than the PCB data alone suggest. 

This would have made subsurface decontamination more

difficult. The surface decontamination results are much more

indicative of how TechXtract would perform in a building

decontamination following a terrorist chemical attack.

The following section describes the use of TechXtract to

decontaminate a large piece of equipment that had been

contaminated with PCBs, polychlorinated dibenzo-p-dioxins

(PCDDs), and polychlorinated dibenzofurans (PCDFs).

Removal of Dioxin Contamination for Gas Turbine

Generator Set Repair

On October 6, 1997, an explosion and fire in Independence, Missouri at the Power and Light

Department Gas Turbine and Electrical Substation No. 1 damaged and contaminated a large gas

turbine generator. The generator needed to be repaired, but first it had to be decontaminated. 

One of two transformers at the substation had exploded, producing a fire that caused capacitors

to rupture also. Wipe samples of the generator showed that it had been contaminated with PCBs,

and with PCDDs and PCDFs that had been produced by the fire. Hexane wipe samples showed

surface levels of PCDDs and PCDFs [in 2,3,7,8-tetrachloro-dibenzodioxin (TCDD) equivalents]

in the range of 3.1 to 24,800 ng per m2

. The cleanup goal for the generator for PCDDs and

PCDFs, so that it could be safely repaired, was 25 ng/m2. 

A contractor was hired to decontaminate the generator and, despite multiple passes with “widely

recognized non-polar solvents,” the cleanup target was not achieved. Leach-back, which EET 

describes as the increase of contaminant levels over time after surface cleanup goals are reached,

caused the concentrations to return to failing levels again. (Although the leach-back

phenomenon might be expected in a porous material, Scott Fay of Active Environmental

Technologies has indicated that the crystal boundaries of a metal can also hold contamination,

leading to leach-back (SAIC, 2003).

EET was then contracted to perform the decontamination of the generator. EET recognized the

significantly hydrophobic nature of PCDDs and PCDFs. To facilitate the water-based

TechXtract decontamination process, an oxidation step was added to the cleanup process. The

Fenton reaction, which produces strongly oxidizing hydroxyl radicals and ozone, was used to

partly oxidize the PCDDs and PCDFs, making them more polar and more soluble. 

Final concentrations of PCDDs/PCDFs are summarized in Table 3.4-3, which compares cleanup

levels with initial contaminant levels. A minimum of 96 percent contaminant removal was

achieved, and the cleanup goal was achieved. 
62

Table 3.4-3. Gas Turbine Generator PCDD/PCDF Wipe Samples Before and After

Sample

Designation

Sample Name Initial

Concentration

(ng/m2

)

Final 

Concentration

(ng/m2)

Change in

Concentration

001TEWS Turbine end plate,

winding side

44.48 0.014 - 99.97%

002GEWS Generator end plate,

winding side

63.4 0.0053 - 99.99%

006LLT Lead line tunnel 544.4 0.39 - 99.93%

007PAF Plenum air flow 24,788. 0.067 - 99.9997%

009RRW W side retaining ring 4769. 0.00 > - 99.9999%

010RRE East side RR 3548. 0.00 > - 99.9999%

016LGE Load gear, East 45.21 0.00 > - 99.99%

017LGT Load gear, Top 21.35 0.00 > - 99.98%

018LGCE Load gear coupling, East 35.02 0.00 > - 99.99%

023SPI-2 South end of pedestal

inside wall

3.1 0.12 - 96%

3.4.5 Concerns for the User

Although TechXtract formulations can contain a variety of organic and inorganic acids, and

organic solvents, EET claims that their spent solutions would not be RCRA characteristic

hazardous waste. However, the spent solutions will take on the characteristics of the

contaminant that is removed. These are some of the ingredients in TechXtract formulations that

necessitate careful handling, based on EET’s Material Safety Data Sheets:

C Sodium hydroxide, 1-5 percent

C Ammonium bifluoride, less than 1 percent

C Phosphoric acid, 1 percent

C Nitric acid, 1-5 percent

C Ethylene glycol monobutyl ether, 5-15 percent

When TechXtract formulations are handled, appropriate personal protective equipment (PPE)

should be worn, including the following:

C Organic solvent resistant impermeable gloves

C Splash apron or rain gear

C Face shield

C Organic solvent resistant impermeable boots.
63

Other PPE may be required, for protection against the contaminants being removed based on a

hazard assessment of site-specific conditions as documented in a Health and Safety plan. 

Most TechXtract formulations are fairly stable on storage at ambient temperatures. Only the

oxidizer-containing formulations are expected to have a limited life, because of the peroxideforming compounds they contain. Their room temperature life expectancy (retaining 70 percent

potency) is about 40 weeks to one year.

3.4.6. Availability of the technology for commercial applications 

EET claims to have used TechXtract decontamination in over four hundred applications, with a

99 percent success rate (EET, 2004). It has been applied to removal of hydrophobic organics

(PCBs, PCDDs, PCDFs) from concrete and steel surfaces, radionuclides from lead surfaces,

organic lead from concrete and granite, inorganic lead and mercury from concrete, and tritium

from concrete.

TechXtract Commercial Products and Services

EET provides decontamination services, and provides training to other companies who want to

perform their own decontamination. 

EET will also provide training on how to perform TechXtract decontaminations. They will sell

TechXtract formulations, customized for a particular cleanup. The formulations sell for $35 per

gal in 55-gal quantities.

Decontamination services are provided by EET, including equipment, formulations, and trained

staff (technicians and supervisor). EET’s average cost for cleanup and disposal of PCBs

(hydrophobic organics), for jobs over 5000 ft2

, is about $4.50/ft2. 

For a PCB cleanup, with relatively uniform surface contamination of about 10,000 :g/100 cm2

,

EET estimates the cleanup price to be $5 to $6/ft2

. This assumes seven to eight treatment cycles. 

Factors increasing the cost of cleanup include:

C Spalled (not smooth) concrete surfaces (about 10 percent increase)

C Walls and ceilings (about 25 percent increase compared to floors)

C Cold temperatures (40 °F cleanups cost about 20 to 30 percent more than 70 °F

cleanups)

C More hydrophobic organics

C Higher contamination levels

C More stringent cleanup concentration goals

C Coated surfaces

C Deep contamination (up to 4 inches).
64

3.4.7 Advantages and Disadvantages

TechXtract has advantages and disadvantages for building decontamination. These are

summarized in the following two sections.

Advantages of TechXtract

The TechXtract technology was designed with minimization of secondary wastes as a design

criterion. The treatment formulations tend to be concentrated, and are applied by hand,

minimizing their volume. Minimal amounts of rinse solutions are also used, and their removal is

enhanced by wet vacuuming. EET often prices cleanups with the disposal of secondary waste

included, giving EET an incentive to minimize the wastes requiring disposal.

Application of the TechXtract technology is relatively simple, and the techniques are not

proprietary (though the formulations are). The technology is simple enough that EET will train a

company’s own staff to use it.

TechXtract can be used to clean solid matrices relatively deeply - up to 4 inches for concrete, for

appropriate levels of contamination. This is a particularly innovative aspect of the technology. 

Most other competing in-place chemical decontamination technologies are only effective for

surfaces.

TechXtract is applicable, with the appropriate formulations, to a wide variety of decontamination

problems:

C Hydrophobic organics

C Heavy metals

C Organometallics

C Radionuclides

C Mixed waste (organics and radionuclides together).

Disadvantages of TechXtract

There are some disadvantages to the use of the TechXtract technology. The surfaces of treated

matrices are abraded and dissolved away to some degree. Concrete surfaces that have been

decontaminated with TechXtract are much more intact, however, than after spalling. Inorganic

fluorides, which are relatively toxic at elevated levels, are used in some TechXtract

formulations. 

The TechXtract formulations are proprietary, so there is a cost that is greater than the raw

materials might be. The selection of formulation ingredients is done by EET based on the

specific application, the contaminants, and the matrix to be decontaminated.

TechXtract has not been tested for effectiveness in decontamination of CWAs from building

surfaces or equipment. Its effectiveness can only be extrapolated from its performance in
65

extracting hydrophobic organics from building and equipment surfaces. These data, presented in

section 3.4.4, suggest that TechXtract would be effective.

3.4.8 Potential Areas for Future Research

The application of the TechXtract technology to clean up building components contaminated

with CWAs needs to be laboratory and field tested. VX, a hydrophobic organophosphate, or an

analogous compound should be tested first. TechXtract has demonstrated its effectiveness for

removal of other hydrophobic organics. Nest, mustard, and a G-agent such as GB, should be

tested. These may be removed fairly readily; their degree of destruction by TechXtract

formulations should also be measured. Thorough study of TechXtract effectiveness for CWAs

would also include tests on both minimally porous surfaces like steel, on painted surfaces, and

on porous surfaces such as concrete and wood.

Section 3.4 References

Borah, 1995. Borah, Ronald E. Methods for removal of contaminants from surfaces. U. S.

Patent No. 5,421,906. June 6, 1995.

Borah, 1996. Borah, Ronald E. Precleaning fluids for use in a process for the removal of

contaminants from surfaces. U. S. Patent No. 5,512,202. April 30, 1996.

Borah, 1998. Borah, Ronald E. De-scaling solution and methods of use. U. S. Patent No.

5,821,211. October 13, 1998.

DOE, 1998. Lead TechXtract Chemical Decontamination. Innovative Technology Summary

Report, DOE/EM-0454. U.S. Department of Energy, Office of Science and Technology (1998). 

Available at http://apps.em.doe.gov/ost/pubs/itsrs/itsr1450.pdf. Accessed November 2004.

EET, 2004. Environmental Extraction Technologies, Inc. Internet web site.

http://www.techxtract.com/about_frame.html. Accessed November 2004.

EPA, 1998. The Superfund Innovative Technology Evaluation Program - Annual Report to

Congress - FY 1997. Report No. EPA/540/R-98/503. U.S. Environmental Protection Agency,

Office of Research and Development. November 1998. Available at

http://www.epa.gov/ORD/SITE/congress/congress.pdf. Accessed November 2004.

SAIC, 2003. Personal communications between W. Scott Fay of Active Environmental

Technologies and William D. Ellis, PhD, of SAIC. July 2003.

Tyerech, 1998. Tyerech, Michael Richard Shelf stable hydrogen peroxide containing carpet

cleaning and treatment compositions. U. S. Patent No. 5,728,669. March 17, 1998.

U.S. Navy, 1997. EET TechXtract Technology Evaluation - Pearl Harbor Naval Complex,

Oahu, Hawaii. Internal report to the U.S. Navy, Pacific Division. April 1997.
66
67

4. FOAM AND GEL TECHNOLOGIES

4.1 Sandia Foam and Decon Green 

4.1.1 Technology Description

Several peroxide-based systems are available for use in the decontamination of buildings,

structures, and equipment. Two specific technologies are discussed in this section: “Sandia

Foam” and “Decon Green.”

A common ingredient to these technologies is hydrogen peroxide (H2O2). Additional discussion

of liquid hydrogen peroxide in non-foam applications is presented in Section 3.4 of this report. 

Most uses for hydrogen peroxide are based on its oxidizing properties and, as such, it becomes a

candidate to consider for decontaminating chemical/biological agents. 

Sandia Foam

Sandia Foam was developed by the Sandia National Laboratories and is manufactured by

EnviroFoam Technologies, Inc. (EFT) under the trade name EasyDECON®, and by Modec, Inc.

under the trade name Modec Decon Formula (MDF) 200®. The Sandia Foam uses a combination

of surfactants and oxidizers to inactivate both biological and chemical agents. These systems

have been shown to be effective against chemical agents, easily applied, and environmentally

friendly. Both Sandia and the West Desert Test Center at Dugway Proving Ground have

reported 7-log (i.e., seven orders of magnitude) kills of Bacillus anthracis spores within one

hour.

The “foam” is somewhat of a misnomer as the chemical can be supplied or created as a foam,

liquid, or aerosol. How the foam kills spores—bacteria in a rugged, dormant state—still is not

well understood. It is thought the surfactants perforate the spore's protein armor and allow the

oxidizing agents to attack the genetic material inside.

Like a fire retardant, the foam could be sprayed from handheld canisters. When the foam is

deployed, it expands to about 100 times its liquid volume through a special nozzle that draws air

into the spray. The foam fills space and contacts chemical or biological agents in crevices and

on open surfaces. In several hours it collapses back to its compact liquid state.

Decon Green

Edgewood Chemical Biological Center (ECBC), Aberdeen Proving Ground, Maryland, patented

a similar peroxide-based system called Decon Green. This system has been demonstrated to be

effective against all chemical agents, easily applied, and is considered to be environmentally

friendly (hence, the name “green”).

This decontamination product is targeted to replace DS2 (Decontaminating Solution 2), the

Army’s non-aqueous decontamination standard.
68

Decon Green is a simple solution of hydrogen peroxide, potassium carbonate, potassium

molybdate, propylene carbonate and Triton X-100® (a non-ionic surfactant) that affords the

rapid, broad-spectrum decontamination of chemical warfare agents, even at low temperatures

(-31 /C). The solution is non-corrosive to common surfaces of military interest and leaves no

toxic residues, so it is considered environmentally friendly. In use, carbonate and molybdate

catalytically activate the peroxide. Thus, the carbonate’s basicity provides peroxy anion OOHto effect the selective perhydrolysis of nerve agents VX and GD to non-toxic products, and both

carbonate and molybdate generate peroxo species which afford oxidation of blister agent HD

(e.g., mustard gas), initially, to the nonvesicant sulfoxide. Besides chemical agents, Decon

Green also affords the destruction of anthrax spores to undetectable levels (as discussed below in

Section 4.1.4). Decon Green and other common decontaminants were tested for efficacy of

chemical agent decontamination of painted surfaces of military interest (Wagner, et al., 2002).

4.1.2 Technical Maturity

Sandia Foam

Vendor data suggest that the Sandia foam systems may be effective against both chemical and

biological agents (see Section 4.1.4). Full scale application to buildings contaminated with

anthrax was tried (see Section 4.1.3). However, testing by EPA using the AOAC Sporicidal

Activity Test on one of Envirofoam Technology’s Products indicated that – contrary to claims

on the product label – the formulation of this product tested at that time was not effective in

decontaminating 6 logs of B. subtillis spores on a hard, non-porous surface at one hour contact

time. As a result, the crisis exemption for EasyDECON and ModecDecon formula was

withdrawn on March 29, 2002.

Decon Green

No detailed scale up information is available. Decon Green has been successfully sprayed using

a standard military decontaminating apparatus (M13) and decontaminant pumper (M21) (ECBC,

undated). It is not clear from the source materials if agent testing was conducted during this

testing.

4.1.3 Applications of the Technology

Applications of Hydrogen Peroxide

Hydrogen peroxide releases oxygen readily, and acts both as a general oxidizing agent and as a

convenient source of readily available active oxygen. Discussion regarding the applications of

aqueous hydrogen peroxide is presented in Section 3.4 of this report. Compared to chlorine (or

ozone, chlorine dioxide, or UV light), H2O2 is a rather poor disinfectant, and is not approved as a

stand-alone treatment for microbial control in water systems. 
69

Applications of Sandia Foam

The Sandia Decon Formulation was on hand for use during high-profile events such as the 2000

Democratic National Convention in Los Angeles, California, the 3rd Presidential Debate in St.

Louis, Missouri (October 2000), and the 2002 Winter Olympics in Salt Lake City, Utah (Sandia,

2002).

Sandia Foam was used as one component in the decontamination of the Capitol Hill complex

following the anthrax-containing letter that was received in Senator Daschle’s suite in the Hart

Senate Office Building (HSOB) in October 2001. In addition to the contamination in the

Daschle suite, surface environmental sampling showed anthrax contamination in several other

suites and common areas on several floors of the HSOB, as well as in filters within two heating,

ventilation, and air conditioning systems that served the Daschle suite. Cross-contamination was

also discovered in several other buildings and mail processing areas. The Daschle suite and the

two ventilation systems serving it were fumigated with chlorine dioxide gas. The other areas

within the HSOB where anthrax had been detected, and the other cross-contaminated buildings

in the Capitol Complex, were cleaned using various surface treatment methodologies. The

primary treatment of these other areas utilized chlorine dioxide liquid or hypochlorite bleach. 

Sandia Foam was used for some initial surface treatments, but was replaced by aqueous chlorine

dioxide and bleach, which were easier to clean up. High-efficiency particulate air filter

vacuuming was sometimes used as a preliminary source reduction step prior to other surface

treatments. Extensive post-remediation environmental sampling at the Capitol Hill site was all

negative for growth of anthrax spores, and on January 22, 2002, the Hart Building was cleared

for re-occupancy (Whitman, 2002).

Although the overall decontamination of the HSOB was successful, the effectiveness of

the Sandia Foam during this process was not specifically evaluated. There were no quantitative

measurements of pre- and post-treatment contamination levels in areas treated solely by Sandia

Foam.

Applications of Decon Green

Decon Green has not been applied outside of a test environment.

4.1.4 Evaluation of Available Data

Solutions of hydrogen peroxide, bicarbonate, and a suitable co-solvent for water-insoluble agents

serve as the basis (activated hydrogen peroxide) for a broad decontamination application for G

agents, VX and HD. More extensive discussion concerning the performance of aqueous

hydrogen peroxide formulations in destroying chemical agents is presented in Section 3.4 of this

report. In particular, Section 3.4 includes data regarding mixtures of hydrogen peroxide and one

or more components of Decon Green (i.e., peroxide activators such as bicarbonate and

molybdate), although no data on the aqueous version of Decon Green itself.
70

Sandia Decon Formulations

Tests conducted at Sandia showed that the foam destroyed simulants of VX, HD, Soman (GD),

and anthrax (Modec, 2003a; Tucker et al., undated).

In October 2000, Sandia was funded by DOE to develop an enhanced version of their foam

(originally called DF-100) to optimize performance for military and civilian first responders

(Modec, 2003b). This resulted in the new decon formulation, DF-200 [Sandia, undated]. Based

on test data, a 99.99999 percent kill of anthrax simulant was achieved after 30 minutes. This

compares with a 99.99 percent kill for DF-100 for the same time period. Modec, Inc. has been

licensed by Sandia to commercially produce DF-200. Modec sells this product as MDF-200. 

Commercial production began in December 2001.

Sandia reported the results of the original and improved formulations. Testing was conducted

using chemical and biological agent simulants. The results are shown in Table 4.1-1. 

Table 4.1-1. Summary Reaction Rates of Agent Simulant Testing –

Versions of Sandia Foam

Formulation 1 minute 15 minutes 60 minutes

HD simulant (2-chloroethyl phenyl sulfide), % decontaminated

DF-100 (pH 8) 18 42 81

DP-100 (pH 9.2) 16 38 83

DF-200 94 98 ND

VX simulant (O-ethyl S-ethyl phenylphosphonothioate, 

DF-100 (pH 10) 45 99 ND

DP-100 (pH 9.2) 33 71 93

DF-200 66 99 ND

G Agent Simulant (diphenyl chlorophosphate)

DF-100A (pH 8) 53 ND ND

DP-100A (pH 9.2) ND ND ND

DF-200 ND ND ND

Anthrax simulant (Bacillus globigii spores)

30 minutes, % kill 60 minutes, % kill

DF-100A (pH 8) 99.99 99.99999

DP-100A (pH 9.2) 90 99.9

DF-200 99.99999 99.99999

Note: ND = below detection limit

Additional live agent testing was conducted at IIT Research Laboratories using test protocols

and DF-200 product supplied by Sandia National Laboratories. The results are shown in Table

4.1-2.

Table 4.1-2. Live Agent Kill Rate Summary (testing conducted at IIT Research Institute)

Agent 1 minute, % kill 15 minutes, % kill 60 minutes, % kill

GD 99.98 +/- 0.01 99.97 +/- 0.01 99.98 +/- 0.01

+/- 0.01VX 91.20 +/- 8.56 99.80 +/- 0.08 99.88 +/- 0.04

HD 78.13 +/- 10.53 98.46 +/- 1.43 99.84 +/- 0.32

Ames RIID* Not measured 99.99999 99.99999

ANR-1* Nor measured 99.99999 99.99999

*Strain of B. anthracis
71

The Modec Decon Formulation (MDF-200) – a similar product also is marketed as EasyDECON

200 by Environfoam Technologies – is actually a three-part system. Part A, a biodegradable

mixture of a cationic surfactant and a fatty alcohol, is formulated from benzyl C12-18 alkyl

dimethyl quaternary ammonium compounds (the surfactant), isopropyl alcohol, and

N,N,N,N',N'-pentamethyl-N’ tallow-1,3-propan-diammonium dichloride. Part B is stabilized

hydrogen peroxide (8%), and part C is glycol diacetate. The foam is composed of 90.7 percent

water, 3.99 percent part B, 1.8 percent part C and the remainder part A.

The Sandia Decon Formulation was field tested at the U.S. Army Proving Grounds at Dugway,

Utah (Sandia, 2003). The field test was designed to test the effectiveness of one formulation in

killing anthrax spores. The anthrax simulant, Bacillus globigii was sprayed onto various panels

(2' x 2') of materials which would commonly be found in a typical office building. Since the

area to be decontaminated was relatively small, and to show versatility, the formulation was

deployed onto the panels as an aqueous spray (using a standard paint sprayer) rather than as a

foam. After 20 hours exposure to the formulation, Dugway personnel tested the panels for

surviving spores. The tests were repeated on four consecutive days, and the results for the

Sandia Decon Formulation indicated the spores were eliminated (see Table 4.1-3). The 20 hour

exposure exceeds the one hour contact time identified on the label direction and used by EPA in

assessing the effectiveness of the product for crisis exemption purposes.

Table 4.1-3. B. globigii (Anthrax Simulant) Spore Kill During Dugway Filed Tests

Surface Contaminated 

(Surface average in CFU*/in.2

)

Decontaminated

(ND = not detected)

Floor (painted concrete) 7.67 x 107 ND

Floor (tile) 1.31 x 107 ND

Floor (carpet) 1.23 x 107 ND

Floor (wood) 7.30 x 106 ND

Window (glass) 5.32 x 104 ND

Painted wall below window 8.16 x 104 ND

Left hand wall panels 4.70 x 104 ND

Wall (stucco) 2.80 x 105 ND

Painted wall above carpet 4.56 x 104 ND

Carpeted wall 1.08 x 106 ND

Door 3.13 x 104 ND

Ceiling 8.49 x 102 ND

*CFU = colony-forming units

The MDF-200 has also been demonstrated to be effective against chemical agents. Testing was

conducted at ECBC, Aberdeen Proving Ground, MD. The decontamination effectiveness is

compared to DS2 (the Army’s non-aqueous decontamination standard). Sandia reports that after

1 hour of contact, 100 percent of the chemical agent was decontaminated (see Table 4.1-4).

Table 4.1-4. Percent Decontamination in Live Agent Testes at ECBC

HD GD VX

Decontaminant 10 min 1 hour 10 min 1 hour 10 min 1 hour

DS2 100 100 100 100 100 100

Sandia Foam (MDF 200) 47 100 >99 100 100 100
72

Sandia has also reported results using the Modec foam against selected Toxic Industrial

Chemicals (TICs). Results are reported in percent decontamination of the TIC (see Table 4.1-5).

Table 4.1-5. Modec Decon Foam against Toxic Industrial Chemicals

TIC

% Decontamination

1 minute 15 minutes 60 minutes

Malathion (liquid) 89 95 BDL

Hydrogen Cyanide (gas) >99 >99 >99

Sodium Cyanide (solid) 93 98 >99

Butyl Isocyanate (liquid) 99 BDL BDL

Carbon Disulfide (liquid) >99 >99 BDL

Phosgene (gas) 98 >99 >99

Anhydrous Ammonia (gas) >99 >99 >99

Note: BDL = below detection limit

The above results of testing with the Sandia Foam formulation – representing information made

available primarily from Sandia National Laboratory, Modec, Inc., and EnviroFoam

Technologies, Inc. web sites – appear to indicate that the decontamination formulation is

effective against chemical and biological agents. It must be noted that no analytical method

detection limits, analytical method description, quality control data, nor test conditions were

available to validate the results as presented. Therefore, no critical review of the results as

presented is possible.

EPA’s testing of Sandia Foam products using the AOAC protocol appears to disagree with the

above results. EPA’s tests were conducted on EasyDECON 4215 (Envirofoam) using Bacillus

subtilis as the test organism. Two media were tested: (1) a porcelain carrier innoculated with 9.2

x 105

 spores; and (2) suture loops innoculated with 2.0 x 106 spores. The carriers were exposed

to EasyDECON 4215 for 60 minutes. The results are shown in Figure 4.1.1.

Since Sandia Foam has an aqueous base, paper products will wrinkle after the solution is applied

and allowed to dry. EasyDECON 200 solution has been tested on a variety of surfaces. 

Concrete, asphalt, wood, ceramic, carpet, fabric, leather, steel and aluminum are just a few of the

many surfaces tested. Bare, steel objects are susceptible to surface rust after application.
73

Suture Loops a:

Contact Time with Suture

Loops

Neutralizer-Primary

Cultures b

# Positive

Secondary Cultures c

# Positive

Total # Carriers (Sets) d

Positive 

60 minutes 9/60 0/60 9/60

Conclusions: Product not effective at 60 minutes. a

 Apparatus was used to hold suture loops in product during contact period. b

 Tubes contain broth (FTM) plus neutralizers. Notation (e.g., 9/60) indicates 9 positive cultures out of 60 samples tested. c

 Secondary tubes (FTM) contain only broth with the carrier.

d

 One carrier set consists of one primary tube and corresponding secondary tube.

Suture Loops a:

Contact Time with Suture

Loops

Neutralizer-Primary

Cultures a

# Positive

Secondary Cultures b

# Positive

Total # Carriers (Sets) c

Positive

60 minutes 59/60 0/60 59/60

Conclusions: Product not effective at 60 minutes. 

a

 Suture loops floated to the surface of the product during contact period.

b

 Tubes contain broth (FTM) plus neutralizers (10 uL of a 10% catalase solution added instead of 10 uL of a 1% catalase

solution). 

c

 Secondary tubes (FTM) contain only broth with the carrier.

d

 One carrier set consists of one neutralizer-primary tube and corresponding secondary tube. 

Porcelain Carriers:

Contact Time with

Porcelain Carriers

Neutralizer-Primary

Cultures a

# Positive

Secondary Cultures b

# Positive

Total # Carriers (Sets) c

Positive

60 minutes 52/60 42/60 52/60

Conclusions: Product not effective at 60 minutes

a

 Tubes contain broth (FTM) plus neutralizers.

b

 Secondary tubes (FTM) contain only broth with the carrier.

c

 One carrier set consists of one primary tube and corresponding secondary tube.

Porcelain Carriers:

Contact Time with

Porcelain Carriers

Neutralizer-Primary

Cultures a

# Positive

Secondary Cultures b

# Positive

Total # Carriers (Sets)

Positive c

60 minutes 33/60 3/60 33/60

Conclusions: Product not effective at 60 minutes

a

 Tubes contain broth (FTM) plus neutralizers (10 uL of a 10% catalase solution added instead of 10 uL of a 1% catalase

solution). 

b

 Secondary tubes (FTM) contain only broth with the carrier.

c

 One carrier set consists of one primary tube and corresponding secondary tube.

Figure 4.1-1. EPA Test Data for EasyDECON 4215
74

Decon Green

Over four years of R&D testing at the ECBC has been devoted to Decon Green, a hydrogen

peroxide-based decontaminant. This universal decontaminating solution for chemical warfare

agents was patented by George Wagner and Yu-Chu Yang (U.S. Patent No. 6,245,957). The

major components include 35 percent hydrogen peroxide solution (30 percent by volume),

propylene carbonate (60 percent by volume), and Triton X-100 (10 percent), a non-ionic

surfactant.

Data show that the perhydrolysis of VX avoids creation of the toxic byproduct EA2192, formed

in generic hydrolysis. Decon Green performed 12 percent better than DS2 when

decontaminating VX on chemical agent resistant coating (CARC) panels. Data also indicate that

Decon Green is more effective in decontaminating painted panels exposed to GB or HD than VX

(Wagner et al. 2002; ECBC, undated). (See Table 4.1-6.) Surface decontamination in 15

minutes was demonstrated to be greater than 99.98 percent using filter paper. Tests have

demonstrated that the solution can decontaminate surfaces contaminated with up to 2.5 x 108 B.

anthracis spores after a 15-minute contact time.

Table 4.1-6. Decontamination of CARC Panelsa

Decontaminant VX GD HD

DS2 72.1% 96.4% 86.7%

Decon Greenb 86.5% 98.0% 90.0%

Notes:

a. 10g/m2

 agent challenge; 30 minute neutralization; CARC=chemical agent resistant coating

b. Decon Green formulated with 50% H202

Laboratory data reported by Wagner and Yang (2002) show how the effectiveness of hydrogen

peroxide against the decontamination of chemical agents is enhanced by the addition of

bicarbonates, carbonates and molybdates. The use of “activated hydrogen peroxide” can be

formulated from food grade materials, formulated for low temperature application and is a fast,

effective decontaminant.

Data regarding the efficacy of Decon Green for B. anthracis is presented by Wagner et al.

(2002). Spore count was reduced from 7 x 107

 to less than 10 in a 10 minute test, resulting in a

greater than 7 log kill. The Decon Green used in the test was formulated at 35 percent hydrogen

peroxide. Testing protocol (e.g., solution versus surface) was not described.

Decon Green is not currently commercially available. It was designed specifically to meet

military needs. Decon Green is based on relatively non-toxic, environmentally acceptable

materials such as baking soda, hydrogen peroxide, and a co-solvent. The product consists of two

solutions plus a catalyst that can be easily mixed using multi-component mixing and storage

system. The decontaminant can be used with fielded decon equipment or commercial off-theshelf high pressure sprayers.
75

4.1.5 Concerns for the User

Typical precautions for hydrogen peroxide should be observed. Material Safety Data Sheets

(MSDSs) for hydrogen peroxide and MDF-200 are available on the web.

Sandia Foam

Sandia claims that the foam represents no hazard, and the foam’s MSDS indicates no reported

significant toxic effects. Respiratory protection may be required if workplace exposure limits

are exceeded. The manufacturer claims that the foam reduces environmental hazards to the point

where the effluent may be disposed of “down the drain.” The foam is non-flammable and

advertised as a dual-use fire-fighting foam and CB decontaminant. [For reference, it is noted

that the commercially available high-expansion Aqueous Film-Forming Foam (AFFF)—a firefighting foam—must be stored and treated as hazardous material.]

Decon Green

This decontaminant is targeted to replace DS2. The current design requires three separate

containers to be mixed prior to use. The Decon Green solution is reported to be non-corrosive to

common surfaces.

4.1.6 Availability of the Technology for Commercial Applications

Sandia Foam

The Sandia Decon formulations can be purchased from the following vendors:

Modec, Inc.

4725 Oakland St

Denver, CO 80239

Toll-free: (800) 967-7887

Phone: (303) 373-2696

Fax: (303) 373-2699

Web: http://www.deconsolutions.com

Envirofoam Technologies, Inc.

2903 Wall Triana Hwy

Huntsville, AL 35824

Toll-free: (800) 542-4665

Phone: (256) 319-0137

Fax: (256) 461-8136

Web: http://www.envirofoam.com

The Modec Decon formula MDF-200 is available in a variety of configurations, as summarized

below:
76

• “Twin-Pak”: boxed set of 5 gallons

• “Quik-Set”: 10 gallon single container

• Single 55 gallon barrel

• Two-55 gallon barrels

• Two-250 gallon Intermediate Bulk Container or tote (IBC)

• Two-350 gallon IBC.

EasyDECON 200 decontamination solution is packaged in several convenient ready to mix

containers. Each container comes ready to use consisting of pre-measured components. 

According to the manufacturer, preparing EasyDECON 200 decontamination solution is fast and

easy and is ready for use within minutes. EasyDECON 200 decontamination solution is

available in various sizes and amounts and is capable of remediating both chemical and

biological contamination.

EasyDECON 200 solution is sold in a variety of sizes and packages. EasyDECON 200 solution

can be purchased in 2.5 gallon containers up to a 250 gallon tote.

EnviroFoam Technologies offers a variety of EasyDECON application equipment including:.

C Fogging systems

- Apply decontamination solution to small enclosed areas

- Adjustable droplet mist

C Handheld pump sprayers

- Apply as a liquid rather than a foam

- Small area decontamination

C MACAW® Backpack compressed Air Foam System

- Manufactured by Intelagard

- Portable self contained compressed air foam system

- 5 gallon capacity

- 35 foot stand-off distance

C Merlin® Handcart Compressed Air Foam (CAF) System

- Manufactured by Intelagard

- Handcart mounted CAF system

- 15 gallon capacity

C EASYCAFS® Foam Delivery Vehicle (FDV)

- Compressed air foam system

- Mounted on a 6x6 Polaris Ranger® all terrain vehicle

- 75 gallon capacity

C Vehicle Mounted EASYCAFS Model 25 Low Profile Slip-in System

- Self contained for truck transportability

- Powered by 19HP air-cooled diesel 
77

Decon Green

Developmental stages are complete and ECBC anticipates that Decon Green will be

commercially available in the near future and available to the military soon after that.

4.1.7 Advantages and Disadvantages

No specific information was found on how the Sandia foam systems were field tested. It is

apparent that the foams can be used in small areas, single rooms, on office fixtures and

equipment. The technologies do not appear to be applicable to HVAC systems.

Sandia Foam

The Sandia Foam decontamination technologies are claimed to have to following advantages:

• Claimed to decontaminate chemical agents

• Claimed to be a general disinfectant for vegetative bacteria and viruses, although

EPA’s AOAC data raise questions regarding its efficacy

• Leaves no persistent toxic residues or toxic by products

• Non-corrosive

• Easy application (no special equipment required)

• Apply as foam, liquid spray or fog

• Relatively rapid reactions – works quickly

• Applicable to various surfaces (though may be a problem for some, such as paper)

• Stable over a wide temperature range including freezing temperatures and hot

surfaces

• Variable shelf life claimed for various formulations; 10-year shelf life claimed for

EasyDECON.

Issues associated with the use of the Sandia Foam decontamination technologies include the

following:

• Efficacy has not been independently verified

• Detailed analytical data need to be reviewed (non-detect value not related to

method detection limits); analytical methodology not available for review

• No detailed scale up information available

• Public safety issues need to be assessed when applied in the field

• Full scale demonstration: efficacy of application to equipment and structures is

uncertain

• Bare, steel objects are susceptible to surface rust after application; paper will

wrinkle

• Potential removal challenges following treatments in civilian settings
78

Decon Green

The Decon Green decontamination technology is claimed to have to following advantages: 

• Leaves no persistent toxic residues

• Non-corrosive

• Easy preparation, no water required

• Easy application (no special equipment required)

• Rapid reactions

• Compatible with cold weather 

• Stable over a wide temperature range including freezing temperatures and hot

surfaces.

Issues associated with the use of the Decon Green decontamination technologies include the

following:

• Efficacy has not been independently verified

• Detailed analytical data need to be reviewed

• No detailed scale up information available (used successfully with M13

decontaminating apparatus and M21 decontaminant pumper).

• Designed for military applications; practicality for building applications needs

further demonstration.

• Public safety issues need to be assessed when applied in the field

4.1.8 Potential Areas for Future Research

Data generated under laboratory controlled conditions show that the Sandia Foam and Decon

Green are effective to some degree in decontaminating chemical and biological agents, but

substantiating data have not been reviewed by EPA. The solutions, therefore, are promising

candidates for additional test and development. Under some conditions, field trials were

conducted with good results.

It is not clear how well the decontamination solution will withstand excessive temperatures and

“dirty” surfaces such as asphalt and concrete. The stability of hydrogen peroxide is understood

from the literature, but actual field test data were not available for evaluation. It is suggested

that a test program be designed to better evaluate the “real world” parameters and effectiveness

of these decontamination systems. 

4.1.9 References for Section 4.1

ECBC, undated. Decon Green Fact Sheet. Edgewood Chemical Biological Center.

Modec, 2003a. Modec Decon Foam – Results Against Selected Toxic Industrial Chemicals. 

Modec, Inc. http://www.deconsolutions.com/TIMS.htm. Accessed November 2004.
79

Modec, 2003b. Performance of the Modec Decon Formulation (MDF-200). Modec, Inc.

http://www.deconsolutions.com/Formulation_accelerated.htm. Accessed November 2004.

Sandia, undated. DF-200 - An Enhanced Formulation for Decontamination and Mitigation of

CBW Agents and Biological Pathogens. Undated draft report.

Sandia, 2002. Sandia Decon Formulation for Mitigation and Decontamination of Chemical and

Biological Warfare Agents. Publication No. SAND2000-0625. Sandia National Laboratory.

http://www.sandia.gov/SandiaDecon/factsheets/overview_apr2002.pdf. Accessed November

2004.

Sandia, 2003. Field Demonstration for Biological Agent Decon (web site).

http://www.sandia.gov/SandiaDecon/demos/demo5.htm. Accessed November 2004.

Tucker et al., undated. Tucker, M.D.; Williams, C.V.; Tadros, M.E.; Baca, P.M.; Betty, R.; and

Paul, J. Aqueous Foam for the Decontamination and Mitigation of Chemical and Biological

Warfare Agents. Sandia National Laboratories, Albuquerque Staff Augmentation Providers, and

Orion International Technologies.

Wagner et al., 2002. Wagner, G.W.; Procell, L.R.; Henderson, V.D.; Sorrick, D.C.; and Yang,

Y.-C. “Decon Green”. Presented at the 23rd Army Science Conference, Orlando, Florida. 2002.

Wagner and Yang, 2002. Wagner, G. W.; and Yang, Y.-C. “Rapid Nucleophilic/Oxidative

Decontamination of Chemical Warfare Agents,” Industrial Engineering and Chemistry

Research, 41 (8): 1925-1928 (2002).

Whitman, Christine Todd. Statement before the Committee on Environment and Public Works,

September 24, 2002. U.S. Environmental Protection Agency.
80

4.2 Canadian Aqueous System for Chemical-Biological Agent Decontamination

(CASCAD®)

The Canadian Aqueous System for Chemical-Biological Agent Decontamination (CASCAD)

was developed in the late 1980s as a classified program under Defence Research and

Establishment Suffield (DRES). In the 1990s the concept was shared outside of the defense

community. The system was originally designed for the decontamination of military equipment

exposed to chemical or biological warfare agents. The formulation was designed to have

minimal effect on materials while inactivating biological and chemical agents. Additional

considerations were to minimize toxicity, maintain compatibility with existing chemical and

biological agent detectors, and to make the formulation a stable foam to enable coatings of

contaminated surfaces for extended periods of time. CASCAD is one of the original eight

decontaminants identified by a study under the Joint Fixed Site Decontamination program by the

U.S. Government. 

4.2.1 Technology Description

CASCAD contains several surfactants in a proprietary mixture in combination with chlorinating

agents. It is a well-published decontamination system that contains Fichlor (sodium

dichlorisocyanurate) as an active ingredient. The mixtures are supplied as a powder and liquid,

packaged separately. The powder is the time-release chlorinating agent that is responsible for

most of the effectiveness of the material. When combined, a foam is generated that is sprayed

on the equipment to be decontaminated. The rigidity of the foam allows for a longer contact

time than pure liquids resulting in improved inactivation of biological and chemical agents. 

The system is extremely scalable, is available in a 20-liter backpack module, and can also be

connected to a fire hose for coverage up to 2,500 square meters per hour. The backpack version

is self-contained and uses air pressure to create the CASCAD foam. In larger applications, water

is added to create the foam. Figure 4.2-1 shows large scale application of the foam. 

A unique feature of this technology is the ability to use water from a variety of sources. The

foam is equally active using distilled water, tap water, non-potable water, and even seawater. 

This degree of versatility minimizes the logistical burden of system implementation. This factor

is also attractive for building remediation because the water supply for the building can be used

for the generation of the foam. Clean up is conducted using a wet-dry vacuum system.

The patented chemical formulations used by NBC Team Ltd. are designed for both blast

mitigation as well as the decontamination of chemical, biological, and radiological compounds. 

The different applications require different formulations. The blast mitigation foam is a much

more dense foam while the radiological formulation is designed to wash off particles and is

much less dense. The formulation for decontamination of chemical and biological agents is

more dense than the radiological, but less dense than the blast mitigation foam. In addition to

the alterations in foam densities, the amount and formulation of the active ingredients are also

tailored to specific applications.
81

Figure 4.2-1. Demonstration of the Foam Application on a Tank Vehicle

4.2.2 Technical Maturity

The CASCAD system is completely mature and ready for operations. The Canadian Defence

Research Establishment originally funded the technology and have transferred the technology for

commercialization. The commercialization team consists of the Defence Research

Establishment Suffield (DRES), The Royal Canadian Mounted Police (RCMP), the National

Research Council (NRC), the U.S. Department of Defense (DoD), George Cowan Enterprises,

O'Dell Engineering Ltd., and NBC Team Ltd. O'Dell Engineering Ltd. was founded in 1995 to

develop and market unique Chemical and Biological weapon decontamination products

worldwide. NBC Team Ltd. is the authorized distributor of products. Their address is:

P.O. Box 11040

921 Barton St.

Stoney Creek Ontario, Canada L8E 5P9

Telephone: 905-643-8801

Fax: 905-643-8824

Email: info@nbcteam.com

Web site: www.nbcteam.com
82

4.2.3 Applications of the Technology

Fichlor is a chemical that is effective in decontaminating chemical and biological agents. 

Chloroisocyanurates are used as disinfectants in general sanitizers, scouring powders, household

bleaches, institutional and industrial cleaners, and swimming pool/ hot tub disinfectants (Kirk

Othmer, 1993). Chloroisocyanurates (sold in granular or tablet forms) are among the leading

swimming pool sanitizing agents in the U.S., with 1992 use of approximately 50,000 tons (Kirk

Othmer, 1998). 

4.2.4 Evaluation of Available Data 

Chemical agent decontamination

Comparative information regarding the effectiveness of the CASCAD system versus well known

decontamination formulations is shown in Table 4.2-1 (published by NBC Team Ltd.). 

Decontaminating Solution 2 (DS2) is 70 percent diethylenetriamine, 28 percent 2-

methoxyethanol, and two percent sodium hydroxide (NaOH). C8, also called the German

emulsion, is 15 percent tetrachloroethylene, 76 percent water, one percent anionic surfactant, and

eight percent calcium hypochlorite, Ca(OCl)2 (National Institute of Justice, 2001). No analytical

data were available for a technical assessment of the decontamination effectiveness.

Table 4.2-1. Comparison of CASCAD to DS2 and C8

Feature DS2 C8 CASCAD

Form as applied Clear liquid Cloudy liquid White Foam

Form as delivered Clear liquid in quart

containers

Multi-part liquid &

powder requiring

emulsifying

Powder and liquid

Additional ingredients None Water Water (fresh, salt, grey)

Destroys agents on surface

Nerve - G, V 

Vesicants - H, L

Biological Agents

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Destroys CW agents in paint Not suitable Not suitable Yes

Toxicity of residue Highly toxic Highly toxic Non-toxic

Effect on typical:

Paint

Rubber

Aluminum

Removes

Softens/breakdown

Pitting

Removes some

Softens

Minor

None

None

None

Tested for removal and

control of radioactive

contamination

Not tested Not tested Best tested

Typical Application Method 20 litre spray 500 gal mixer

requires approx. 30

minutes

Continuous injection system

reloadable without shutdown.

Draw from any available

water source

 a. Based on Canadian Forces testing and publications. CW agents which contain arsenic will retain less toxic

arsenic compounds in the residual material. 

 b. Liquid nature of DS2 and C8 makes it difficult to remain in contact with surfaces and effectively remove agent

without destroying surface finishes.

 c. Canadian Forces and French Government test results.

Source: NBC Team Ltd. (Vanguard Response Systems, Inc.) http://www.nbcteam.com/products_decon_index.shtml
83

Table 4.2-2, published by NBC Team Ltd. (now Vanguard Response Systems, Inc.), reports the

effectiveness of CASCAD against standard chemical warfare agents. The amount of chemical

agent used at the start of the experiment is not reported. This makes the evaluation of the data

very difficult.

Table 4.2-2. CASCAD Effectiveness Against Chemical Warfare Agents 

Agent Time (minutes) Percentage of agent remaining

 Nerve Agent GA 1 <0.56

3 0

Nerve Agent GB 1 <0.56

3 0

Nerve Agent GD 1 Trace

3 0

5 0

10 0

Nerve Agent VX 6 -

7 0

11 0

Blister Agent HD 3 <0.05

5 -

19 -

Source: Vanguard Response Systems, Inc.

The company states that all tests were conducted at unspecified independent government

laboratories. While that is certainly accepted, the data presented in this fashion without specific

experimental details have limited utility.

Biological Agent Decontamination

A series of experiments were conducted by the Canadian government to determine the

effectiveness of CASCAD for the killing of Bacillus anthracis (Anthrax) spores. Ames strain of

B. anthracis was prepared by culture on blood agar plates followed by transfer of the bacteria

into a buffer solution. The suspension was heated to 60 degrees Celsius for one hour to kill all

vegetative organisms. A suspension of spores was distributed onto a metal plate and allowed to

dry overnight. Plates were covered either with a control foam or the CASCAD formulation and

incubated for thirty minutes at room temperature. Plates were rinsed and then the spores

removed by wiping with a sterile cotton swab. Spores were dispersed in growth medium and

aliquots were streaked onto blood agar plates for subsequent colony counts. A four log reduction

in spore viability was demonstrated after a thirty minute contact time.

These experiments compared the effects of CASCAD with control foam containing no active

ingredients. It is not known what the effect of the control foam was on the bacterial spores. 

Although this experiment did not control for spores washing off the plate during incubation and

subsequent rinsing, since both populations of plates were treated similarly, these errors most

likely canceled out during the experimentation process (Kourmikakis, Purdon and Chenier,

2000). 

Compared with the control foam, the CASCAD product demonstrated a four-log (99.99 percent)

killing of the Bacillus anthracis spores. Although this does not meet the U.S. EPA’s Federal
84

Insecticide, Fungicide, and Rodenticide Act (FIFRA) sterility requirement, it does meet the

North Atlantic Treaty Organization (NATO) decontamination requirement. 

In a separate publication from DRES, the effect of CASCAD on Bacillus globigii spores was

evaluated. The authors concluded that CASCAD was a very effective decontaminant (Spence,

undated). While the conclusion appears to be supported by the data, the data are qualitative and

not quantitative. Therefore one can not calculate a log reduction factor from these results. 

Table 4.2-3 presents product information published by the commercial vendor of CASCAD

indicating effectiveness against biological material. No tests have been reported against any

toxins or toxic industrial compounds.

Table 4.2-3. Effectiveness of CASCAD Treatment

Agent Time of exposure (minutes) Percentage of agent remaining

viable

Bacillus globigii spores 5 0.0001%

 " 60 0.000001%

Erwinia 5 0.000001%

Bacillus anthracis spores 30 0.001%

 " 30 0.011%

Source: Vanguard Response Systems, Inc.

Evaluation of “Rapid Lightning Report”

Rapid Lightning was a biological warfare simulant sampling and decontamination exercise

funded by the Defense Threat Reduction Agency in August of 1999. CASCAD killing

efficiency was evaluated for the BW simulants Bacillus globigii (Bg) spores, and Erwinia

herbicola (Eh) vegetative bacteria. This exercise represented the first evaluation of CASCAD in

the U.S. These laboratory trials were a series of experiments that varied the mix of CASCAD to

simulant in ratios from 10:1 to 0.5:1, with contact times ranging from five to 60 minutes. No

comparisons were conducted against any other decontamination technology with the exception

of 5 percent bleach. CASCAD effectiveness was determined by measuring the number of

colony forming units (cfu) in the presence and absence of CASCAD. A six log reduction was

considered effective decontamination. 

The data presented support the use and further evaluation of CASCAD as a decontamination

protocol for spore remediation. The data presented in the Rapid Lightning report do not provide

standard error measurements. This degree of resolution is essential because of the apparent

variability of the protocol. In the Rapid Lightning study, CASCAD at a 1:1 ratio for a 60 minute

exposure demonstrates an eight log reduction of Bg spores, while the same experimental

conditions yielded only a 2.5 log reduction. The authors proposed this variability was due to

different spore preparations. However, it is unlikely that spore preparation could adequately

explain such a divergence in results. Accordingly, additional experimentation is required to

determine the actual effectiveness against a spore population.

Experiments with the vegetative bacteria, Erwinia herbicola, demonstrated a seven log reduction

at a 1:1 volume ratio even after only five minutes contact time. These data are consistent with
85

the accepted fact that vegetative bacteria are much more susceptible to destruction than the

bacterial spore.

4.2.5 Concerns for the User

According to results published by the Canadian Government, the residue from CASCAD is

non-toxic. Unlike some of the harsher decontaminants like DS2, CASCAD is reported not to

harm paint, rubber, or aluminum surfaces. While the material in the formulation of the foam

does not appear to be toxic to users, one must recognize that the target of the remediation is

harmful to the user. Therefore, the user should employ personal protective equipment while

using this product. A user should consult the MSDS for the active ingredient in CASCAD,

MILCON-T.

4.2.6 Costs

CASCAD products are available commercially. The fully integrated system that can be hooked

up to a fire truck or other water source retails for $85,000. Intermediate sized systems are also

available. A portable backpack sprayer is $2,500. Coverage areas as a function of deployment

system are not mentioned. However decontamination for 10 square feet of surface requires one

liter of CASCAD. Operational costs range from $0.30 to $0.60 per square foot depending on

quantity ordered. These operational costs are for outside equipment decontamination. Use

within a building could have significantly greater operational costs, based on recent experience

in decontaminating some buildings impacted by the 2001 anthrax mail incident.

4.2.7 Advantages and Disadvantages

CASCAD is a demonstrated technology for remediation of chemical and biological warfare

agents. The product was designed for the military for use in battlefield environments. 

Demonstrations have been on the exteriors of tanks, ships, and aircraft. In these situations the

product performs as stated. This product was not developed as a building interior remediation

alternative. 

With the recent terrorist attacks with Bacillus anthracis spores in envelopes, the CASCAD

vendor has claimed value for this product in such applications. The value claimed is two-fold. 

The first is in limiting the spread of the biological or chemical agent. The foam acts as an

insulator to prevent further dissemination. The second effect is the decontamination. While this

may be a useful approach for rapid isolation, it is much more invasive and destructive than

fumigation due to the wet nature of the product and the need to remove after application. These

are vendor claims that have not been evaluated by the EPA.

CASCAD, as well as other foam based decontamination alternatives, is very labor intensive

when applied to building interiors. Sandia Foam was used for remediation of the Dirksen and

Ford Office Building mailrooms in the fall of 2001; a material expected to have a consistency

similar to CASCAD. Not only was the foam not fully effective, the clean up operations were

extensive and time consuming (personal communication with the Coast Guard personnel

conducting remediation operations). 
86

The most significant advantage to a system of this type is immediate isolation and containment

of the exposed area. Application of this type of technology could have significant impact on

spread of the contamination.

4.2.8 Potential Areas for Future Research

The CASCAD formulation is mature for chemical and biological decontamination operations. 

Additional documentation by independent researchers would validate the vendor's claims. The

concept for utilization of this type of a product for initial isolation is quite promising, but not

validated by experimentation. The data presented in this report are very suggestive of efficacy,

but more rigorous experimental conditions are required.

4.2.9 References for Section 4.2

Kirk-Othmer, 1998. Encyclopedia of Chemical Technology, Fourth Edition, Volume 25, “Water

(Treatment of Swimming Pools, Spas, and Hot Tubs).”

Kirk-Othmer, 1993. Encyclopedia of Chemical Technology, Fourth Edition, Volume 7,

“Cyanuric and Isocyanuric Acids.”

Kourmikakis et al., 2000. Kourmikakis, B; Purdon, J.G; and Chenier, C.L. Verification of

CASCAD in the Decontamination of Bacillus anthracis Spores. Report ECR-2000-141. Defense

Research Establishment, Suffield. 2000.

National Institute of Justice, 2001. Guide for the Selection of Chemical and Biological

Decontamination Equipment for Emergency First Responders: Volume I. NIJ Guide 103-00,

Volume I, U.S. Department of Justice. October 2001. 

Spence, undated. Spence, M.; Ho, J.; and Ogston, J. Decontamination of Vehicle Using

CASCAD After Exposure to Biological Aerosol Hazards.
87

4.3 L-Gel

L-Gel is a spray-on decontamination gel that has been found effective to some degree against

both toxic chemicals and biological agents. The following sections describe how it works,

laboratory and field test results, and practical considerations for its use.

4.3.1 Description of the Technology Alternative

L-Gel is a decontamination technology developed at Lawrence Livermore National Laboratory

(LLNL) with three important characteristics: 

C It oxidizes chemical warfare agents (CWAs)

C It kills bacterial spores used as biological warfare agents (BWAs)

C It sticks to vertical and overhead surfaces. 

Raber and McGuire, of the Environment Protection Department at LLNL, have reported on the

development and testing of L-Gel (Raber and McGuire, 2002; LLNL, 2002; Raber and McGuire,

undated). It is non-toxic, non-corrosive, easy to manufacture (and therefore relatively

inexpensive), and easy to deploy (LLNL, 2002). The oxidizing agent in L-Gel is Oxone®, a

Dupont Corporation patented triple salt with the following formula (DuPont 1998a):

2KHSO5CKHSO4CK2SO4

The active ingredient in Oxone is the first component of the triple salt, and is called potassium

peroxymonosulfate. The peroxymonosulfate anion is a moderate strength oxidizer, strong

enough to oxidize a halide anion to a halogen (neutral) or a hypohalite anion, a ferrous cation to

ferric, and a manganous cation to manganic (DuPont 1998a). 

Oxone has been shown in laboratory studies to oxidize VX to ethyl methylphosphonic acid

(EMPA) and diisopropyl taurine (Yang, Baker, and Ward, 1992):

MeP(=O)(OEt)SCH2CH2N(iPr)2 + 3KHSO5 +H2O o 

VX Potassium Water

 Peroxymonosulfate

MeP(=O)(OEt)OH + HO3SCH2CH2N(iPr)2 + 3KHSO4

Ethyl Methyl- Diisopropyl Potassium

phosphonic Acid Taurine Bisulfate

where Me = methyl, Et = ethyl, iPr = isopropyl. 

The sulfur in the thiol ester link in VX is oxidized to a sulfonic acid functional group, producing

the two products from VX that are much less toxic than VX. Potassium bisulfate is a neutral salt

with very low toxicity. 
88

Figure 4.3-1. L-Gel, Delivered as Semisolid, is Liquified for

Use

Source: LLNL, 2002.

The gelling agent in L-Gel is Cab-O-Sil® EH-5, a synthetic amorphous colloidal silica (silicon

dioxide) made by Cabot Corporation (LLNL, 2002). Cab-O-Sil EH-5 has an average particle

length of just 0.2-0.3 μm (Cabot, 2002). When Cab-O-Sil EH-5 is added (15 percent) to an

aqueous solution of Oxone, a gel is formed that can be applied to surfaces using paint spraying

equipment. After application, it begins to dry and thicken, so that it adheres well to walls and

ceilings.

L-Gel is packaged as a high-viscosity, gelatin-like semi-solid, as shown in Figure 4.3-1, that is

liquified by shaking or stirring. The liquified product can be applied using paint spraying

equipment that is commercially available (Raber, 2002). The researchers note that due to LGel’s acidic properties, stainless steel spray nozzles must be used (Raber and Maguire, 2002).

Decontamination with L-Gel takes about 30 minutes after application. L-Gel eventually dries

out completely, in about one to six hours, to a residue that can be removed by vacuuming. 

4.3.2 Technical Maturity 

L-Gel has been tested for decontamination of BWAs and CWAs, in the laboratory and in the

field (see Section 4.3.4). It is not yet commercially available. It has been developed in three

different forms: 

C L-Gel 115 was the first decontamination gel developed by LLNL

C L-Gel 200, an improved version of L-Gel 115, is being developed to have the

ability to penetrate coatings of paint or varnish

C An aerosol version of L-Gel is being developed for decontamination of the

interior of ventilation systems.

LLNL is negotiating with several companies to license the manufacturing and marketing of LGel. 
89

The cost for L-Gel is estimated at about $1 to cover 1 m2

, which is about 11 ft2 (LLNL, 2002). 

Labor, equipment, and mobilization will be additional costs. 

4.3.3 Applications of the Technology 

The active ingredient in L-Gel is Oxone, a commercial product of Dupont used for oxidation of

organics. Dupont literature cites the use of Oxone in numerous applications (DuPont, 1998b),

including:

• Denture cleaners contain at least 25 percent Oxone, which provides stain removal.

• Pool and spa shock treatments in which Oxone is used as an auxiliary oxidant. In this

application, Oxone is not a disinfectant. 

• Pool and spa disinfectants, when used in a two-part combination with sodium bromide. 

A mixture of 80 percent Oxone to 20 percent sodium carbonate for the first step is

recommended as a means to control the pH. This application is registered under FIFRA. 

• Repulping recycled papers, which uses Oxone as an alternative to chlorine-containing

repulping agents. 

• Printed circuit board etching, which uses Oxone in combination with acid and

temperature controls to achieve etch rates of 0.25 to 2.5 :m/min (10 to 100 : in/min).

• Wool shrinkproofing as a replacement to chlorine applications. 

• Laundry bleach as an alternative to hypochlorite provided the concentration of Oxone in

the water is at least 25 ppm. 

• Treatment of reduced sulfur or cyanides in waste streams. 

On March 5, 2001, DuPont announced that it planned to increase the supply of Oxone to meet

demand from its customer, Antec International (DuPont, 2001). Antec manufactures Virkon® S,

a disinfectant used to prevent the spread of foot and mouth disease in the United Kingdom. 

4.3.4 Evaluation of Available Data 

Oxone Test Results

Oxone, the oxidizing agent in L-Gel, was tested by LLNL for its effectiveness in

decontaminating surrogates for three types of BWA:

C Bacillus subtilis (for anthrax and other spore-forming pathogens)

C Pantoea hericola (for plague)

C Ovalbumin (for botulinum toxin).

Oxone was more than 99 percent effective in oxidizing the surrogates, which had been applied to

common building materials such as carpet, wood, and stainless steel (LLNL, 2002).
90

In similar tests, Oxone was equally effective at treating surrogates for three CWAs:

C Amiton, or S-[2-(diethylamino)ethyl] O,O’-diethylphosphorothioate (for VX)

C Diphenyl chlorophosphate (for sarin, GB)

C Chloroethyl ethyl sulfide (for sulfur mustard, HD).

The HD surrogate was 100 percent oxidized in 10 min by double the molar amount of Oxone. 

The VX surrogate was 93 percent oxidized in 30 min, and more than 99 percent oxidized in 40

min. Based on the work with Oxone for oxidation of HD and VX performed by Yang, Baker,

and Ward (1992), the effectiveness of Oxone in oxidizing the LLNL surrogates was expected. 

The same researchers, however, showed that G agents are only slowly hydrolyzed by Oxone

solutions, and not oxidized at all. LLNL found diphenyl chlorophosphate to be 100 percent

destroyed in the time allotted. (The amount of time was not given. Destruction was probably

through acid catalyzed hydrolysis, since Oxone solutions are strongly acidic.) 

Battelle (1999) reports that the active ingredient in Oxone, potassium peroxymonosulfate,

rapidly oxidizes VX and does not form EA2192 as a by-product like VX hydrolysis does. Also,

HD is oxidized to the sulfoxide immediately, and then to the sulfone within an hour. These are

less toxic products. Battelle reports that Oxone can only decontaminate or detoxify the G agents 

by slowly hydrolyzing them by acid catalysis. Battelle is citing the results reported by Yang,

Baker, and Ward (1992) that showed hydrolysis half-lives of about 50 and 80 min for 0.03 M

GB and 0.02 M GD, respectively, in 0.1 M Oxone at pH 2. (Note that it takes seven half-lives to

reduce a starting material by 99 percent, and ten half lives to reduce starting material by 99.9

percent.)

L-Gel Laboratory Tests with CWAs

The final design formulation of L-Gel, called L-Gel 115, was tested at LLNL against CWA

surrogates on materials commonly found in buildings: varnished wood, painted steel, glass,

fiberglass, and carpet (LLNL, 2002). (Presumably, the same surrogates were used as those

described above for LLNL’s testing of Oxone alone.) The L-Gel was applied to each agentcontaminated test surface, allowed to dry for 30 min to several hours, and then surrogate residual

levels were determined. L-Gel 115 was found to be more than 99 percent effective for all agents

on all surfaces.

L-Gel was laboratory tested by two other organizations against real CWAs during the period

from October to November, 1999:

C Edgewood Chemical and Biological Forensic Analytical Center, Maryland, US

C Defense Evaluation and Research Agency (DERA), Porton Down, United

Kingdom (UK).

At Edgewood, L-Gel’s decontamination effectiveness was tested on acrylic-painted metal,

polyurethane-coated oak flooring, and indoor-outdoor carpet surfaces. The tests showed that LGel was more effective for decontamination of 2.5 μl samples of VX (2.53 μg), GD (soman;

2.52 μg), and HD (3.18 μg) than calcium hypochlorite, a CWA decontaminating agent
91

commonly used by the US military. The CWAs were placed on the substrates for 15 min, then

L-Gel was applied and allowed to dry for 24 hr. Samples were collected, extracted with 10 mL

of dichloromethane, and the extracts were analyzed. Agent decontamination was complete in all

but the GD tests on acrylic- and polyurethane-coated surfaces. All VX and HD was treated, with

detection limits of 0.1 μg/mL for VX and GD, and 1.0 μg/mL for HD. (If it is assumed that the

extracts were concentrated to 1 mL before analysis, the treatment effectiveness for “complete”

decontamination can be calculated by the reader to be at least 96 percent for VX and GD, and 69

percent for HD.) 

At Porton Down in the UK, L-Gel was laboratory tested for its decontamination effectiveness on

thickened GD (TGD) and thickened HD (THD) applied to about 3 by 5 inch metal plates painted

with either alkyd or polyurethane paint. The thickened CWAs were applied to the test surfaces 1

hr before decontamination. L-Gel 115 was then applied to the metal plates in a vertical position

with a commercial compressed air paint sprayer. After 30 min, the sample plates were sprayed

with ambient temperature high pressure water, then soaked in isopropanol for 2 hr, and the

extracts were analyzed. (One would assume that the untreated control plates were also sprayed

with high pressure water, and that the analyses represented only the agent remaining that had

diffused into the paint.) L-Gel 115 decontaminated 35 percent of the TGD and 50 percent of the

THD in the alkyd paint, and 64 and 66 percent in the polyurethane paint, respectively. 

To be effective, a technology must not only clean the contaminated surface but also reach below

the polymeric paint to treat CWA that penetrated the surface during the attack or as a result of

surface cleaning. The Porton Down test required L-Gel to demonstrate effective treatment of the

thickened agents on the surface as well as treatment of contaminants below the surface of the

polymeric paints within 30 minutes. The 30-minute period allowed in the Porton Down test is

not adequate time and seems to be an impractical test. Complete removal of the paint layer

would seem to be more appropriate if rapid decontamination is important. Alternatively,

multiple applications of L-Gel, with gentle heating of the paint layer to enhance diffusion, might

be considered. (See section 3.2, in which TechXtractis applied many times for difficult

decontaminations.) This is the only test conducted with L-Gel that specifically required

subsurface decontamination. The solution suggested by the developers of L-Gel, for further

development, was incorporation of a co-solvent. They said that this might “eliminate the

problem with gelled chemical agents.” The problem may also exist on any painted horizontal

surface, with any agent persistent for at least 1 hour. Interestingly, the Porton Down study data

did not include results for any other decontamination method for comparison.

L-Gel Laboratory Tests with BWAs

L-Gel 115 was also tested at LLNL against BWA surrogates on varnished wood, painted steel,

glass, fiberglass, and carpet, as with CWA surrogate tests (Raber and McGuire, 2002; LLNL,

2002). The L-Gel was applied to each agent-contaminated test surface, allowed to dry for 30

min to several hours, and then surrogate residual levels were determined. L-Gel 115 was found

to be more than 99 percent effective for all agents on all surfaces.
92

LLNL also performed in vitro tests of two safe (nonvirulent) strains of the biological warfare

agents (BWAs) Bacillus anthracis (spore form) and Yersinia pestis (bacteria): Sterne and Strain

D27, respectively. The agar plate resistance test is a standard test for measuring the efficacy of

antibiotics. L-Gel was more than 99.9 percent effective in killing the spores and bacteria

(LLNL, 2002).

L-Gel Field Tests with CWAs

L-Gel was field tested by the Military Institute of Protection in Brno, Czech Republic against

real CWAs during October, 1998. L-Gel 115 was tested outdoors on aged (more than 20 years

old) concrete, new concrete, aged asphalt, and new asphalt. The performance of L-Gel was

compared with a standard water solution of high test hypochlorite (HTH), for treatment of GD

and VX (the latter on new substrates only). Agent was deposited on a circular area of about 20

m2

 using a hand sprayer, at a density of about 15 g/m2. After 2 hr, untreated agent samples were

collected. The decontaminant was then sprayed on about 5 m2, allowed to remain in contact for

30 min, then 25 cm2

 samples were collected and analyzed. L-Gel showed 98, 98, and 70 percent

agent destruction for GD on new and old asphalt and for VX on new asphalt, respectively; HTH

showed 80, 95, and 72 percent destruction for the same agent-substrate combinations. L-Gel

showed 100, 98, and 99 percent agent destruction for GD on new and old concrete and for VX

on new concrete, respectively; HTH showed 100, 95, and 95 percent destruction for the same

agent-substrate combinations. In summary, L-Gel was slightly more effective than the standard

HTH decontamination solution in four tests; equal in one test; and slightly less effective in one

test.

L-Gel Field Tests with BWAs

In December, 1999, L-Gel was field tested on surrogate bacterial spores at the U.S. Army

Soldier Biological and Chemical Command (SBCCOM) facility at Dugway Proving Ground in

Utah. Initial surrogate organism counts on 40 cm2 panels of acoustic ceiling tile, tightly woven

fabric, fabric-covered office partition, painted wallboard, concrete slab, and painted metal were

about 107 spores/10 cm2. L-Gel was applied, and allowed to stand for 24 hours. Swabs samples

of the panels were collected, and live spore counts were reduced by an average of 99.988

percent, and a minimum of about 99.96 percent (LLNL, 2002) (See Table 4.3-1). 

 

Table 4.3-1. Surrogate Spore Counts Before and After L-Gel Treatment*

Test Panel Material Spore Count Before Spore Count After Reduction

Cement 2 x 106 5 x 102 99.98 % 

Ceiling 1.5 x 106 6 x 102 99.96 % 

Panel fabric 4 x 106 5 x 102 99.99 % 

Painted metal 4 x 106 1 x 102 99.998 %

Painted wallboard 6 x 106 4 x 102 99.993 %

Carpet 3 x 106 1 x 102 99.997 %

* Level of detection was 1 x 102

 spores. Counts were averages of five trials, for areas of 10 cm2. Before and After

counts were estimated for this table from a logarithmic-scaled graph of results (LLNL, 2002).
93

In October, 2000, LLNL staff took part in another surrogate BWA test at Dugway in which a

full-scale mock office with different floor and wall materials was contaminated and

decontaminated. The floor materials were carpet, vinyl tile, varnished oak, and painted

concrete. Wall materials included stucco, wood paneling, plasterboard, and carpet. The ceiling

was suspended ceiling tile.

The office was contaminated with 4 g of Bacillus subtilis spores by a simulated explosion using

a disseminator; then the spores were further spread by an oscillating fan. L-Gel was used to treat

the room, then 400 swab samples were collected from throughout the office. Swabs were

quenched in sterile, buffered sodium thiosulfate solution. (This would use up any remaining

oxidizing capacity of the L-Gel. With this care in controlling the period of treatment, it is

surprising that no treatment time data were provided.) Quenched samples were plated and live

colonies were counted. The detection limit was 100 colony-forming units (cfu) per 4 in2

 (4

cfu/cm2

). L-Gel reduced the spore counts by about five orders of magnitude and did not damage

office surfaces, except that it created some surface rust on ceiling supports. In comparison,

paraformaldehyde was similarly effective at reducing the live spore counts (Raber and McGuire,

2002; LLNL, 2002).

Research indicates that L-Gel does not harm carpets or painted surfaces (LLNL, 2002), however

as noted earlier, L-Gel does have acidic properties that require the application of the material

with a stainless steel sprayer nozzle. 

4.3.5 Concerns for the User

The pH of L-Gel is approximately 4 (LLNL, 2002). Like other decontamination technologies

discussed in this publication, appropriate caution should be taken to avoid exposure to both the

treatment chemical and the target chemical/biological agent. Users should ensure that all

appropriate personal protective equipment are used. 

Oxone is an acidic oxidizer that is corrosive to the eyes, skin, nose, and throat. DuPont states

that they observe a 1mg/m3

, 8-hour time-weighted average airborne exposure to Oxone (DuPont,

1998a). Oxone is incompatible with halide or active halogen compounds, cyanides, transition

heavy metals, and oxidizable organics (DuPont 1998a).

4.3.6 Availability of the Technology for Commercial Applications

L-Gel is not commercially available. Licensing discussions are underway between Lawrence

Livermore National Laboratory and potential vendors.

4.3.7 Advantages and Disadvantages

L-Gel has a number of advantages over other decontamination technologies. It can be used for

both CWA and BWA decontamination. As a general purpose oxidizer of organic compounds, it

can be expected to be effective against a wide variety of hazardous industrial chemicals as well.
94

It has the advantage over decontamination solutions that it is in gel form, so that it will adhere to

vertical and overhead surfaces like walls and ceilings. The oxidizing power of Oxone tends to

reduce hazardous compounds to less toxic oxidation products, but this must be ascertained on a

chemical-by-chemical basis.

L-Gel 200 has the ability to penetrate into polymeric coatings like paints and varnishes, an

important capability for decontaminating persistent CWAs that have soaked into surface

coatings. Without this ability, decontaminated surfaces will continue to become re-contaminated

as subsurface agents gradually diffuse back to the surface. This phenomenon has been referred

to as “leach-back” (see section 3.2.4), and is a potential problem for decontamination of most

surfaces, including coated or porous surfaces, and even steel.

Application of L-Gel to decontaminate a surface is relatively simple: commercially-available

spray painting equipment can be used. L-Gel’s estimated cost of $1 (materials only) to treat an

area of 1m2 (11 ft2

; LLNL, 2002) is quite reasonable. Applying L-Gel is simple, so labor costs

will not be high.

The disadvantages of L-Gel include: (1) It is not available commercially; (2) The residual salts

and silica significantly increase the mass of the waste produced, which may have hazardous

properties, depending on what products are formed in the oxidation by Oxone; (3) The efficacy

of the product against anthrax spores needs to be tested further to determine whether it meets

EPA’s pesticide registration requirements.

4.3.8 Potential Areas for Future Research

L-Gel is being developed along two lines: (1) Penetration into surface coatings to prevent leachback (L-Gel 200); and (2) Making L-Gel available as an aerosol for decontamination of the

interior of ventilation systems. These improvements will be significant advantages for the L-Gel

technology.

Minimizing the mass of amorphous silica used to form the gel would be another area with

potential benefit for commercializing L-Gel. Research into the ability of L-Gel decontamination

wastes to be solidified, such as by silicate or Portland cement stabilization, would be useful for

controlling the costs of waste disposal, an important component of the overall cost of the

technology.

4.3.9 References for Section 4.3

Battelle, 1999. Wide Area Decontamination: CB Decontamination Technologies, Equipment

and Projects - Literature Search and Market Survey. Report to the U.S. Joint Service Materiel

Group by Battelle Memorial Institute and Charles W. Williams, Inc. March 1999.

Cabot, 2002. “Overview of CAB-O-SIL Untreated Fumed Silicas.” Cabot Corp. web site:

http://www.cabot-corp.com/cws/product.nsf/PDSKEY/~~~EH5/$FILE/CAB-O-SIL_EH5.pdf. 

Accessed November 2004.
95

DuPont, 1998a. “DuPont Oxone Monopersulfate Compound Technical Information.” E. I.

duPont de Nemours and Company web site:

http://www.dupont.com/oxone/techinfo/index.html. Accessed November 2004.

DuPont, 1998b. “DuPont Oxone Monopersulfate Compound Applications.” E. I. duPont de

Nemours and Company web site: http://www.dupont.com/oxone/applications/index.html. 

Accessed November 2004.

DuPont, 2001. “DuPont Steps Up Efforts with UK’s Antec to Battle Foot and Mouth Disease

Epidemic in Europe.” March 5, 2001. http://www.dupont.com.au/ag/news/070301.html. 

Accessed November 2004.

LLNL, 2002. “Science and Technology Review: L-Gel Decontaminates Better Than Bleach.” 

April 2002. Lawrence Livermore National Laboratory web site:

http://www.llnl.gov/str/March02/Raber.html. Accessed November 2004.

Raber and McGuire, undated. Raber, Ellen; and McGuire, Raymond. “Gel-Based Universal

Oxidation for CB Decontamination.” Chemical and Biological Defense Information Analysis

Center Access No. CB-188538.

Raber and McGuire, 2002. Raber, Ellen; and McGuire, Raymond. “Oxidative decontamination

of chemical and biological warfare agents using L-Gel,” Journal of Hazardous Materials, B93:

339-352. 2002.
96

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97

5. GAS AND VAPOR TECHNOLOGIES

5.1 Chlorine Dioxide Gas

As a biological sterilizer, chlorine dioxide (ClO2) reacts as an oxidizing agent. The predominant

target of its oxidizing action is thought to be the protein of the bacteria or virus. Oxidation of the

protein molecules is thought to lead to functional disruption. Although the exact mechanism of

this process is not fully characterized, data exist demonstrating the antimicrobial effects of ClO2

on many common surfaces. ClO2 is a relatively unique oxidizing agent in that it functions by

single-electron transfer. Unlike chlorine, it does not react with organics to form harmful

chlorinated products such as trihalomethane (THM) and chloramines.

Although its name and chemical formulation suggest a close relationship with chlorine gas (Cl2),

this is not the case. ClO2 gas is not stable under high pressures, and therefore cannot be stored in

high-pressure cylinders as most gases are. ClO2 is readily soluble in water, and is stable for

extended periods of time in this form. Unlike chlorine, ClO2 remains a true gas in solution. This

lack of significant interaction with water molecules is partly responsible for the effectiveness of

ClO2 over a wide pH range.

5.1.1 Description of the Technology 

Chlorine dioxide gas is generated at the decontamination site (as discussed below), and injected

into sealed building areas. It is allowed to remain in place for the required period of time,

typically on the order of 12 hours. When treatment is complete, the chlorine dioxide is

neutralized, for example, by circulating the building air through a sodium sulfite/bisulfite

solution.

Chlorine dioxide gas has been registered as a sterilant under the Federal Insecticide, Fungicide,

and Rodenticide Act (FIFRA) since 1988. However, it is not registered for use against anthrax

in building applications. Accordingly, EPA needed to grant crisis exemptions for its use in

response to the 2001 anthrax events. Site-specific crisis exemptions were issued for each of the

four sites that were fumigated with ClO2 gas – the Hart Senate Office Building (HSOB); the U.S.

Postal Service’s mail processing and distribution centers in Washington, DC (“Brentwood”) and

Trenton, NJ (“Hamilton”); and the Boca Building in Boca Raton, Florida. Prior to issuance of

the first exemption, conditions for chlorine dioxide fumigation were established using a trailer

test facility at Brentwood. Based upon the trailer tests and the experience with the initial

fumigations, the conditions specified on EPA’s web site (EPA, 2004) for ClO2 fumigation of a

building to treat for anthrax are:

 • Target ClO2 concentration and exposure time: 750 ppm for 12 hours, for a total

concentration times time multiple (CT) of 9,000 ppm-hours;

 • Minimum temperature: 70 o

F (the most recent crisis exemption, for the Trenton facility,

specified 75 o

F)

 • Minimum relative humidity (RH): 65 percent (the most recent exemption specified

75%). 
98

Although the three ClO2 fumigations indicated above utilized one particular ClO2 generation

technology, the gas could potentially be generated on-site by one of several technologies. 

Commercial ClO2 gas generators are available in a range of sizes, although most have not been

demonstrated at the scale required to treat a large building. Many of the alternative chemical

reactions that are utilized by different vendors to generate ClO2 gas are illustrated in Section

5.1.2 below (ERCO, 2004).

5.1.2 Methods for the Generation of Chlorine Dioxide

ClO2 from Sodium Chlorite: 

 1. Acidification of chlorite

5 ClO2

–

 + 4 H+ 6 4 ClO2 + 2 H2O + Cl–

 2. Oxidation of chlorite by chlorine

2 NaClO2 + Cl2 6 2 NaCl + 2 ClO2 

 3. Oxidation of chlorite by persulfate

2 NaClO2 + Na2S2O8 6 2 ClO2 + 2 Na2SO4

 4. Action of acetic anhydride on chlorite

4 NaClO2 + (CH3CO)2O 6 2 ClO2 + NaClO3 + NaCl + 2 CH3CO2Na

 5. Reaction of sodium hypochlorite and sodium chlorite (Sabre Technologies)

NaOCl + 2 NaClO2 + 2 HCl 6 2 ClO2 + 3 NaCl + H2O

 6. Electrochemical oxidation of chlorite

ClO2

– 6 ClO2 + e–

 7. Dry chlorine/chlorite (laboratory method)

NaClO2 + 1⁄2 Cl2 6 ClO2 + NaCl (solid)

ClO2 from Sodium Chlorate:

 8. Reduction of chlorates by acidification in the presence of oxalic acid

2 HClO3 + H2C2O4 6 2 ClO2 + 2 CO2 + 2 H2O

 9. Reduction of chlorates by sulfur dioxide (Mathieson Process)

2 NaClO3 + H2SO4 + SO2 6 2 ClO2 + 2 NaHSO4

10. ERCO R-2® and ERCO R-3® processes

NaClO3 + NaCl + H2SO4 6 ClO2 + 1⁄2 Cl2 + Na2SO4 + H2O

11. ERCO R-5® process

NaClO3 + 2HCl 6 ClO2 + 1⁄2 Cl2 + NaCl + H2O
99

12. ERCO R-8® and ERCO R-10® processes

3 NaClO3 + 2 H2SO4 + 0.85 CH3OH 6 3 ClO2 + Na3H(SO4)2 + H2O + 0.05 CH3OH

+ 0.6 CHOOH + 0.2 CO2

13. ERCO R-11® process

NaClO3 + 1⁄2 H2O2 + H2SO4 6 ClO2 + NaHSO4 + H2O + 1⁄2 O2

In all of the above reactions ClO2 gas is one of the products generated from one of the two parent

compounds, chlorite (ClO2

–

) or chlorate (ClO3

–

). The selection of a particular process is

determined by what materials are available, what side products are useful to the specific

industry, and the need for efficiency of the process. Individual manufacturers also have their

favorite processes and will adapt them to the situational need.

There are two basic concerns when choosing a synthesis method for chlorine dioxide. These are

the amount of gas needed and the safety concerns of the precursors and byproducts. The

electrochemical generation of chlorine dioxide from a ClO2

–

 salt (Equation 6 above) presents the

fewest safety concerns. Systems are commercially available that can generate from two to fifty

pounds of gas per day.

Larger quantities can be generated by both “wet” and “dry” processes. The dry process passes

chlorine gas through a solid bed of NaClO2, thereby generating pure chlorine dioxide gas. 

There are two concerns with this process. The first is the transportation and storage of chlorine

gas. Some manufacturers dilute the chlorine in nitrogen for safety reasons. The second concern

is the possible “channeling” of chlorine gas through the solid bed resulting in the release of

chlorine gas.

The wet process used for the HSOB, Brentwood, and Hamilton reacted hydrochloric acid and

sodium hypochlorite to generate chlorine gas, followed immediately by reaction of the chlorine

gas with a solution of sodium chlorite to produce ClO2 (effectively, Equation 5 above).

The last two processes are frequently used in commercial applications. The chemical reactions

between the chlorine and chlorite in the two processes are chemically identical. The “gas:solid”

process (as termed by CDG technologies) – Equation 7 above – does not use liquids. The Sabre

Technologies approach employs a two-step process within a single reactor (Equation 5), using

the chemicals in water. These reactions are presented in more detail in Table 5.1-2 later in this

report.

All three of the above processes, when operated properly, are claimed by the vendor to generate

pure chlorine dioxide gas without contaminating chlorine gas. The systems are all designed not

to have impurities in the product, allowing for accurate comparisons of the different usages of

the gas produced. By-products of the reactions remain in either the solid or liquid phases of the

reaction.
100

5.1.3 Applications for Chlorine Dioxide

Chlorine dioxide was first discovered in the early 1800s by Sir Humphrey Davy, who reported

the reaction of sulfuric acid with potassium chlorate (Davy, 1811). The gas exists in air as a

yellow-green gas with a molecular weight of 67.5.

The vast majority of applications of chlorine dioxide utilize the gas dissolved in water. Wood

pulp bleaching is the largest use of chlorine dioxide, accounting for an estimated 95 percent of

the chemical’s production. ClO2 was used for water odor problems at Niagara Falls in the 1940s

(McCarthy, 1945). This first successful application led to its use in other water treatment

facilities. The widespread use of ClO2 for water purification developed later as a result of

studies in the 1970s that linked chlorine, the preferred disinfectant of the time, with cancer

(Alavanja et al., 1980; Cantor, 1997; Page et al., 1976). The cancer causing effect of chlorine

was linked to the formation of THM as a disinfection by-product (Roe, 1976). Researchers had

previously conducted comparisons between ClO2 and chlorine, and determined ClO2 to be quite

effective for water purification without the generation of harmful by-products found with

chlorine (Synan et al., 1975; Bernard et al., 1976a and 1976b; Ridenour and Armbruster, 1949).

Chlorine dioxide is used to treat drinking water in approximately 5 percent of the water

treatment facilities in the United States serving more than 100,000 people (ASTDR, 2004). 

However, throughout Europe, chlorine dioxide is commonly used as a disinfectant in distribution

systems (ERCO, 2004). In drinking water supplies, chlorine dioxide is utilized as a primary or

secondary disinfectant, for taste and odor control, total trihalomethane/ haloacetic acid

(TTHM/HAA) reduction, iron and manganese control, color removal, sulfide and phenol

destruction, and Zebra mussel control. Aqueous solutions of chlorine dioxide will release

gaseous chlorine dioxide into the atmosphere above the solution. Some newer generators

produce a continuous supply of dilute gaseous chlorine dioxide in the range of 100 to 1,000

mm Hg (abs) instead of using an aqueous solution. Aqueous solutions in the range of 0.1– 0.5

percent are common in a number of current generation technologies used in potable water

treatment processes (EPA, 1999). As in the pulp and paper industry, chlorine dioxide is

preferred over chlorine in some instances due to a reduced formation of chlorinated organic

compounds. These results led to the EPA’s suggestion in 1983 to use ClO2 as an effective

disinfectant. Partially as a result of these actions, the number of applications to use ClO2 for

water purification grew to 200-300 in the U.S. and thousands in Europe (Aieta and Berg, 1986).

While the initial commercial use for ClO2 was water purification, the utility of this gas

expanded. ClO2 is now used in the paper processing industry (Balcer, 1981), fruit and vegetable

processing industries (Anon, 1977; Costilow et al., 1984), and the dairy (Oliver et al., 1989),

poultry (Baran et al., 1973; Lillard, 1979; Thiessen et al., 1984), and beef (Emsweiler et al.,

1976) industries. ClO2 is not as reactive as chlorine and therefore is more stable in wastewater

environments because it has fewer reactive targets in solution. As a result, it is also used in

industrial waste processing facilities (EPA, 1979; Rauh, 1979; Freymark and Rauh, 1978).

The gaseous form of chlorine dioxide is the form most frequently employed as a fumigant.

Chlorine dioxide gas was registered by the EPA as an antimicrobial sterilant in the 1980s. It is
101

registered for sterilizing manufacturing and laboratory equipment, environmental surfaces, tools,

and clean rooms. It is also used in pharmaceutical research and production. Another use of

chlorine dioxide gas is in the washing of fruit and vegetables. Published research studies

indicate that chlorine dioxide gas can effectively kill Listeria monocytogenes cells on apple skins

and reduce bacteria in the stem cavity and in the calyx (Du et al., 2002). Liquid chlorine dioxide

formulations were registered in the 1960's as a disinfectant. It is used in this manner on pets and

farm animals, in bottling plants, and in food processing, handling and storage plants. Other

industrial uses of chlorine dioxide gas and liquid formulations include: bleaching textiles,

disinfecting flume water, disinfecting meat and poultry, disinfecting food processing equipment,

sanitizing water, controlling odors, and treating medicinal wastes.

Whether aqueous or gaseous in form, chlorine dioxide is produced at the point of application. 

Due to its instability, chlorine dioxide is not transported in pure form as a compressed gas. 

Instead, it is generated from sodium chlorite or sodium chlorate (solid or aqueous materials that

are easily transported and stored), according to one of the reactions in Section 5.1.2 above. 

Gaseous chlorine dioxide is explosive at concentrations above 10% by volume in air (10 kPa, or

76 mm Hg, partial pressure at 1 atmosphere total pressure). Chlorine dioxide solutions are

normally stored cold at concentrations of less than 10g/L in order to keep the concentration of

gaseous chlorine dioxide above the aqueous solutions below the explosive limit. These solutions

are corrosive to the skin and eyes, and must be handled with adequate ventilation. Protective

equipment required for the handling and application of chlorine dioxide include impervious

clothing, neoprene gloves and boots, gas-tight chemical splash goggles and face shields, and

other appropriate clothing to prevent the contact of skin with aqueous solutions or vapor. 

NIOSH/OHSA-approved respiratory protection is required for chlorine dioxide concentrations

above 0.1 ppm. Self-contained breathing apparatus is required for entry and escape, and in

firefighting, when ClO2 concentrations are above 10 ppm or are unknown (Kirk-Othmer, 1993).

The application of gaseous chlorine dioxide for building contamination was demonstrated in the

remediation of the Hart Senate Office Building (HSOB), the Brentwood Mail Processing and

Distribution Center (P&DC), and the Trenton P&DC following the 2001 release of anthrax

spores through the mail.

5.1.4 Evaluation of Available Data

5.1.4.1 Data from laboratory and trailer testing

Testing by the pharmaceutical industry

Prior to the 2001 anthrax mail attacks, the pharmaceutical industry conducted extensive testing

of ClO2 for its toxic effect on bacteria, viruses and spores in pharmaceutical sterilization

applications.

In one such test program, the Sterilization Science and Technology section of Johnson &

Johnson tested the efficiency of ClO2 for the destruction of bacterial spores. These experiments

were conducted under controlled laboratory conditions using a 316-liter research sterilizer. The
102

results presented in Table 5.1-1 were conducted using inlet gas pre-humidified to 70-85 percent

RH and an operating temperature of 30-32 oC, with the targets for decontamination being spore

strips containing 106

 spores of B. subtilis.

Table 5.1-1. Effect of ClO2 Gas Concentration on the Rate of Inactivation of 106 B. subtilis

Spores on Paper Stripsa

Exposure Time Fraction Nonsterileb

(Minutes) 10 mg/L 

(3,000 ppm)

20 mg/L 

(6,000 ppm)

40 mg/L 

(12,000 ppm)

0 NT 20/20 19/20

15 NT 19/20 1/20

30 20/20 4/20 0/20

60 9/20 0/60 0/20

90 3/60 NT NT

180 0/20 NT NT

240 0/20 0/20 NT a

 The paper spore strips were placed next to the foil suture package and then overwrapped with Tyvek/Mylar. b

 NT = not tested

Based upon these data, the following were the minimal concentration-time (CT) values

determined to be required for complete sterilization of the spore strips at three ClO2

concentrations, where CT is the concentration of ClO2 gas in ppm multiplied by the duration of

exposure in hours.

 • 3 hours x 3,000 ppm = CT value of 9,000; 

 • 1 hour x 6,000 ppm = CT value of 6,000; and 

 • 0.5 hours x 12,000 ppm = CT value of 6,000.

Following these initial experiments, the Johnson & Johnson scientists postulated that the same

gas could be employed utilizing a flexible-wall barrier isolation system. The scientists

conducted geometry testing using indicator strips located at various regions within the chamber

and concluded that within “reasonable limits”, a ClO2 gas generation system is unaffected by the

size or location of targets within the structure. 

The Johnson & Johnson researchers also concluded that ClO2 did not appear to leave a residue

on the sterilized surface, as is observed with some other gaseous sterilants. Not only is the

residue non-observable, but the gas itself breaks down very rapidly. Beginning with a

concentration of 3,000 ppm at start, there was only 2 ppm remaining at 15 minutes and less than

0.5 ppm after 30 minutes. While this is a benefit for removal of ClO2 from a system after

sterilization is completed, it also clearly points to the need for a robust system that can generate

the gas at the required amounts for the required time during the sterilization process. This effect

becomes increasingly more important as larger structures are used.
103

EPA-Sponsored Evaluations of ClO2 for Anthrax Decontamination – Testing at Dugway

Chlorine dioxide fumigation was one of the remediation steps selected to decontaminate some of

the buildings impacted by the anthrax-containing letters that were introduced into the U.S. mail

system in October 2001. To help determine the appropriate ClO2 fumigation conditions for

treating treat B. anthracis, to be incorporated into the crisis exemptions for treatment of these

facilities, EPA’s Regional Office in Denver, Colorado – in cooperation with EPA’s Office of

Pesticide Programs (which is responsible for issuing the crisis exemption) – contracted the West

Desert Test Facility at Dugway Proving Ground to test the effects of ClO2 on a variety of dried

Bacillus spores:

 • BAA – Bacillus anthracis var. ames,

 • BAV – Bacillus anthracis var. vollum,

 • BAS – Bacillus anthracis var. sterne,

 • BGN – Bacillus subtilis var. niger, 

 • BT – Bacillus thuringiensis, and

 • BST – Bacillus stearothermophilus.

The data discussed and illustrated below were excerpted from West Dugway Test Center, 2002. 

For these tests, spores from three strains of Bacillus anthracis (BA) and three BA simulants were

dried on either glass slides or porous filter paper and exposed to chlorine dioxide gas for 1, 2, 4,

6, 8, and 12 hours at different relative humidities (30 to 92 percent). Temperature was not

specifically controlled; discussions with the Dugway team indicated that they operated at

ambient temperatures (70-75 /F).

Spore preparations were cultured and a liquid slurry was applied to either porous filter paper or

glass slides and dried. Triplicate slides or filter paper were removed from the sterilization

chamber at specific intervals and cultured to determine presence of viable spores. Experiments

were conducted at various chlorine dioxide concentrations as well as various relative humidity

values.

The Dugway team noted that – at ClO2 concentrations between 125 and 1,050 ppm – the relative

humidity is very important for killing all three strains of BA spores. The authors recommend a

relative humidity of greater than 70 percent for effective spore killing activity.

The authors stated that the spores dried on the glass slides were more resistant to the

remediation. This is understandable, since the spores are known to clump when wet and most

likely provided a level of insulation for spores farther away from the air interface. The spore

preparations on the filter papers were not subjected to analysis because the majority

demonstrated a six-log kill after only one hour under most conditions. It is important to note that

the filter paper preparations were most like the conditions at the HSOB. The spore preparation

in the envelope received at HSOB was reported to be very dry. It is possible that some spore

clumping occurred in regions where sampling was conducted, but this was likely minimal.
104

Figure 5.1-1. Log of Colony Forming Units (cfus) Remaining at Each Time Point

for Trial 11; Laboratory Validation of Chlorine Dioxide Decontamination

Another interesting finding from the Dugway report is that their data using spores of Bacillus

subtilis var. niger were sufficiently variable such that these data could not be included in the

analysis. B. subtilis v. niger is the same strain often used on the spore strips that are utilized in

the field to validate the chlorine dioxide remediation.

Figure 5.1-1 presents Trial 11 of the Dugway testing. This figure indicates that, at 30 percent

RH, a modest concentration of ClO2 has no measurable effect on viability of any spore type

tested. Figure 5.1-2 presents Trial 9 – also at 30 percent RH, but at a much higher concentration

of ClO2 (1,050 ppm) – there is still no significant loss of viability over time for any of the

organisms, except for the BGN spores. These data support the authors’ conclusion that BGN

may be the most susceptible spore tested against ClO2. However, the Dugway tests were only a

range-finding study, using only three spore strips or carriers per run. As a result, this analysis of

BGN’s relative susceptibility is not statistically definitive.

NOTE: BAA – Bacillus anthracis var. ames, BAV – Bacillus anthracis var. vollum, BAS – Bacillus anthracis var.

sterne, BGN – Bacillus subtilis var. niger, BT – Bacillus thuringiensis, BST – Bacillus stearothermophilus.
105

Figure 5.1-2. Log of Colony Forming Units (cfus) Remaining at Each Time Point

for Trial 9; Laboratory Validation of Chlorine Dioxide Decontamination

NOTE: BAA – Bacillus anthracis var. ames, BAV – Bacillus anthracis var. vollum, BAS – Bacillus anthracis var.

sterne, BGN – Bacillus subtilis var. niger, BT – Bacillus thuringiensis, BST – Bacillus stearothermophilus.

Figure 5.1-3 presents Trial 5, which utilized an intermediate concentration of ClO2, 613 ppm, at

60 percent RH. Even at this higher RH value and at a moderate concentration of ClO2, still only

BGN was susceptible to the gas. These data support the conclusion that an RH above 60% is

needed for ClO2 to be effective in this application.

Figure 5.1-4 presents Trial 1, which utilized an intermediate concentration of ClO2, 650 ppm, at

a still higher RH of 75 percent. Under these conditions, the BGN was again most susceptible,

although the other organisms are now also showing clear susceptibility. No viable spores were

observed of any organism after 12-hour incubation. These conditions correlate to a CT value of

7,500 ppm-hr.
106

Figure 5.1-3. Log of Colony Forming Units (cfus) Remaining at Each Time

Point for Trial 5; Laboratory Validation of Chlorine Dioxide Decontamination

Figure 5.1-4. Log of Colony Forming Units (cfus) Remaining at Each

Time Point for Trial 1; Laboratory Validation of Chlorine Dioxide

Decontamination

NOTE: BAA – Bacillus anthracis var. ames, BAV – Bacillus anthracis var. vollum, BAS – Bacillus anthracis var.

sterne, BGN – Bacillus subtilis var. niger, BT – Bacillus thuringiensis, BST – Bacillus stearothermophilus.
107

Figure 5.1-5. Log of Colony Forming Units (cfus) Remaining at Each Time Point

for Trial 10; Laboratory Validation of Chlorine Dioxide Decontamination

Figure 5.1-5 clearly identifies relative humidity as the most critical parameter for the ability of

ClO2 to kill Bacillus spores. At a relatively low concentration of ClO2, 250 ppm, and at a 90

percent RH, there were essentially no viable spores of any type remaining after two hours of

exposure. These conditions were more than twice as effective as the data with a RH of 75

percent and a greater than two-fold increase in ClO2 concentration.

NOTE: BAA – Bacillus anthracis var. ames, BAV – Bacillus anthracis var. vollum, BAS – Bacillus anthracis var.

sterne, BGN – Bacillus subtilis var. niger, BT – Bacillus thuringiensis, BST – Bacillus stearothermophilus.

These experiments conducted at Dugway Proving Grounds clearly demonstrate the importance

of relative humidity, time and ClO2 concentration for the killing of dried Bacillus spores. The

Dugway testing was not completed in time to help define the concentration, time, and RH to be

specified in the crisis exemption allowing ClO2 fumigation during remediation of the HSOB. 

However, these data validated the values selected for the HSOB fumigation, and have supported

the conditions specified for subsequent fumigations.

The data presented above were for spores dried on glass slides. The scientists also conducted

parallel experiments using the same spore slurry dried on filter paper. The spores on the filter

paper possibly had a greater exposed surface area, since they were adhering to the threedimensional fiber matrix of the paper. The data obtained from the filter paper indicated almost

100 percent killing of all spore types within one hour under almost all experimental conditions. 

It was suggested that the higher kill rate on the paper might be due to the potential ability of the
108

gas to penetrate the paper from both sides, whereas the spores applied to glass slides could be

attacked only from one side. Another possibility is that clumping of the spores may have been

more likely on the glass slides, where the high-concentration spore slurry would have resided in

a pool as the liquid dried; the clumps could have been more resistant to the ClO2.

EPA-Sponsored Evaluations of ClO2 for Anthrax Decontamination – Washington, DC, Test

Trailer

Since the Dugway testing could not be completed before the decisions had to be made

regarding ClO2 fumigation conditions for the HSOB, a brief series of tests was conducted in the

Washington, DC, area to help define these conditions.

The tests utilized a trailer-mounted Sabre Technologies ClO2 generator, piped to fumigate an

adjacent empty truck trailer (Schaudies et al., 2003). Spore strips and Steri-charts containing

three B. anthracis surrogates – B. subtilis, B stearothermophilus, and B. thuringienisis – were

placed inside the trailer. The average ClO2 concentration to which the indicators were exposed

was varied between 200 and 2,300 ppm over the series of 12-hour runs, giving CT values

ranging from 2,000 to 28,000 ppm-hr. The average relative humidity inside the trailer was

varied between 65 and 79% for different runs. The average temperature inside the trailer was

held at 75 to 78 o

F. Prior, preliminary lab tests conducted by DoD’s Defense Advanced

Research Products Agency (DARPA) had suggested that a CT above 4,000 ppm-hr, an RH

above 75%, and a temperature above 75 o

F would be preferred; the range of conditions for these

trailer tests were selected on that basis.

Based on the results of these tests – and subsequent analysis – it was decided that the target ClO2

fumigation concentration should be 750 ppm for 12 hr (CT = 9,000 ppm-hr), and that the RH and

temperature should be “as high as possible” (Schaudies et al., 2003). Of the three spores tested,

B. subtilis was the most susceptible to the ClO2 gas.

EPA-Sponsored Evaluations of ClO2 for Anthrax Decontamination – Beltsville Maryland

After fumigation of the HSOB, EPA conducted a series of seven fumigations in a trailer at the

U.S. Department of Agriculture’s (USDA) Agricultural Research Center in Beltsville, MD to

decontaminate U.S. mail and private carrier packages transferred from the P Street Warehouse,

as well as artifacts, critical items (items determined to be too important for destruction), and

other items that were not treated with ethylene oxide sterilization. The two photographs in

Figure 5.1-6a and 5.1-6b illustrate the chlorine dioxide generation system and the interior set up

at the Beltsville remediation facility.

The first six runs were conducted between March 22 and March 28, 2002. The seventh run was

conducted on April 10 and 11, 2002. The target exposure concentration was 1,000 ppm for 9

hours in runs one through six. In the seventh run, the target ClO2 concentration was 450 ppm for

a longer exposure time of 20 hours. Uncontaminated packaging materials were included in the
109

Figure 5.1-6a. Chlorine Dioxide Generation System at Beltsville, MD

last run to determine the penetration efficiency and other effects of ClO2 on various materials. 

The target temperature for all runs was approximately 80 /F, with a target relative humidity of

80-85 percent. Actual measurements were taken for all three parameters at frequent intervals

during each run and are presented and discussed below.

Spore strips were used to assess the effectiveness of the fumigations. As with other fumigations,

B. subtilis and B. stearothermophilus were used. A combination of spore strips and Steri-charts

were placed in 30 designated sampling locations in the treatment trailer during each run. The

effectiveness of each fumigation was assessed using a total of 255 spore strips. Each array

consisted of a negative control strip, three B. subtilis spore strips and one B. stearothermophilus

spore strip. Steri-charts were included at half of the sampling locations, along with an additional

negative control strip. Spore strips were in a Tyvek sleeve and all samples were handled with

powder-free, sterile, nitrile gloves and alcohol-sterilized tweezers to prevent crosscontamination. Each spore strip included a location code and a unique identification number. 

Positive controls from each Steri-chart were used to assess viability of the spores on the test

strips. Therefore, they were removed and placed in a pre-labeled key envelope prior to

positioning of the charts and were never exposed to ClO2 gas.

Sporicidal efficiency was calculated for each individual run for each of the two indicator

organisms. The use of the steri-chart strips allowed for quantification of kill efficiencies of up to

108

 for B. subtilis and 107 for B. stearothermophilus. Fractional exponents were calculated based

on the raw data. In some cases there was positive growth at 106

 with both higher concentrations

being growth negative. This could be the result of clumping on the spore strip, or handling

and/or laboratory error. If the sample was subsequently analyzed by culture and the resultant

organisms were not the indicator species, the culture data were considered growth negative. 

There were no cases in which growth of the target organism occurred after exposure to the lower

concentrations of chlorine dioxide fumigant.

5.1-6b. Interior Operations at ClO2 Test

Facility at Beltsville
110

Two Beltsville 3D bar graphs were generated illustrating five factors: relative humidity,

temperature, concentration of chlorine dioxide integrated over time (CT), log kill rate, and

organism type (Figure 5.1-7, B. subtilis, and Figure 5.1-8, B. stearothermophilus). The graphs

were generated from data in the table inserts shown on the figures. The graphs present kill rate,

concentration of chlorine dioxide integrated over time (CT), and percent relative humidity

(percent RH) on three axes. The fumigation temperatures are color coded in incremental ranges

from <75.1 o

F (blue) to >85 oF (red). The organisms are identified with different patterns on the

bars of the graph. B. subtilis has vertical lines and B. stearothermophilus has horizontal lines. 

The same scaling was used on the axes of the two graphs to allow for easier comparison.

Temperature and Relative Humidity Data. Temperature and relative humidity values were

calculated by taking the average of the readings for each data run from two machines, Model No.

8762, for the “Black” version (Serial No.: 01120527) and the “Grey” version (Serial No:

01120217). The temperature and humidity values used ranged from the time of initial treatment

of ClO2 to the final reading. After the average was obtained for each machine, an average of the

two values was taken for the final temperature and relative humidity value listed for each test

run. 

Concentration Data. Concentration values were calculated by taking the average of the final

concentration readings of the four sample locations for each test run. 

B. subtilis var. niger was originally selected as a surrogate organism, because of its unique

property of producing an orange color on agar growth plates. This makes the identification of

this particular strain relatively easy in a subsequent culture analysis.

Run #1

The first run resulted in a chlorine dioxide CT value of 9,920 over a 9.7-hour period with an

average concentration of 1022 ppm/hr. The average temperature was 85.7 oF with an average

RH of 86 percent. All of these values were within the target range. The kill rate for B. subtilis

was 107.5 and the kill rate for B. stearothermophilus was 106

. These results were consistent with

earlier data in which the killing efficiency for B. subtilis was generally an order of magnitude

greater than that achieved for B. stearothermophilus under identical conditions.

Run #2

The second run resulted in a relatively high chlorine dioxide CT value of 15,345 over a 12-hour

period with an average concentration of 1,278 ppm/hr. The average temperature was 82.4 o

F

with an average RH of 85 percent. All of these values were within the target range. The kill rate

for B. subtilis was 106 and the kill rate for B. stearothermophilus was also 106

. These results

were inconsistent with earlier data in which the killing efficiency for B. subtilis was generally an

order of magnitude greater than that achieved for B. stearothermophilus under identical

conditions.
111

Beltsville—B. subtilis

Test Run %RH Temp (/F) CT Kill Rate Run Duration

(hours)

CT/Hour

1 86.0 85.7 9,920 107.5 9.7 1022

2 82.4 84.6 15,345 106 12.0 1278

3 81.1 84.4 12,578 107.2 9.0 1397

4 83.8 85.7 9,772 108 7.7 1269

5 83.8 84.1 10,325 107.7 8.0 1290

6 86.3 87.4 12,722 107.8 9.0 1413

7 79.3 80.2 14,374 107.6 21.0 684

Temp Range Color Key

<75.1 

75.1-77.5 

77.6-80.0 

80.1-82.5 

82.6-85.0 

>85.0 

Figure 5.1-7. Beltsville data for Bacillus subtilis spore strip analysis at various conditions
112

Beltsville—B. stearothermophilus

Test Run %RH Temp (/F) CT Kill Rate Run Duration

(hours)

CT/Hour

1 86.0 85.7 9,920 106 9.7 1022

2 82.4 84.6 15,345 106 12.0 1278

3 81.1 84.4 12,578 106.4 9.0 1397

4 83.8 85.7 9,772 106.4 7.7 1269

5 83.8 84.1 10,325 106.8 8.0 1290

6 86.3 87.4 12,722 107 9.0 1413

7 79.3 80.2 14,374 107 21.0 684

Temp Range Color Key

<75.1 

75.1-77.5 

77.6-80.0 

80.1-82.5 

82.6-85.0 

>85.0 

Figure 5.1-8. Beltsville data for Bacillus stearothermophilus spore strip analysis at various

conditions.
113

The efficiency in killing of B. stearothermophilus during the second run at the Beltsville location

is analogous to the results from Run 1. The efficiency of killing B. subtilis was notably low in

the second run. The temperature and humidity were within the target range. The CT value was

actually 50 percent higher than the target level. The elevated chlorine dioxide concentration

would lead one to predict a better killing efficiency based on previous data. In fact, the killing

efficiency was six logs, but this was still below all other runs. Upon careful evaluation of the

spore strip analysis, a potential explanation is evident. On this run the spore strips appear to be

grouped by type and number of organisms rather than by location. For all other runs the spore

strips were analyzed in groupings by location rather than by type. Stated in another way, spore

strips containing the same amount of a particular bacterial spore were processed together. As a

result of this organization, the spore strips containing 107

 and 108 spores were processed at the

end of the run. All of the last 21 samples prior to the positive controls demonstrated growth,

including a negative control that was also positive.

An artifact in the strip processing may have created this large cluster of positive cultures. With

the available data, it is impossible to determine the source of the contamination. None of these

positive cultures was analyzed to determine if the bacteria were the same bacteria as present on

the original spore strip. 

Run #3

The third run resulted in a chlorine dioxide CT value of 12,578 over a 9-hour period with an

average concentration of 1,397 ppm/hr. The average temperature was 84.4 o

F with an average

RH of 81 percent. All of these values were within the target range. The kill rate for B. subtilis

was 107.2 and the kill rate for B. stearothermophilus was 106.4. These results were consistent with

earlier data in which the killing efficiency for B. subtilis was generally an order of magnitude

greater than that achieved for B. stearothermophilus under identical conditions. 

Overall, runs 1-3 had the lowest killing efficiencies for both target organisms. 

Run #4

The fourth run resulted in a chlorine dioxide CT value of 9,722 over a 7.7-hour period with an

average concentration of 1,269 ppm/hr. The average temperature was 83.8 o

F with an average

RH of 86 percent. All of these values were within the target range. The kill rate for B. subtilis

was 108 and the kill rate for B. stearothermophilus was 106.4. These results were consistent with

earlier data in which the killing efficiency for B. subtilis was generally an order of magnitude

greater than that achieved for B. stearothermophilus under identical conditions.

While this run had the lowest CT value, it had the most effective kill rate for B. subtilis. The

killing efficiency for B. stearothermophilus was also high, but not the highest in the series. The

high temperature and relative humidity may have been responsible for the enhanced

performance.

Run #5

The fifth run resulted in a chlorine dioxide CT value of 10,325 over an 8-hour period with an

average concentration of 1,290 ppm/h. The average temperature was 84.1 oF with an average
114

RH of 84 percent. All of these values were within the target range. The kill rate for B. subtilis

was 107.7 and the kill rate for B. stearothermophilus was 106.8. These results were consistent with

earlier data in which the killing efficiency for B. subtilis was generally an order of magnitude

greater than that achieved for B. stearothermophilus under identical conditions.

The operating conditions for runs 4 and 5 are essentially identical and the killing efficiency in

the two runs is not notably different. Thus, the results may illustrate the range of values that can

be expected under nearly identical conditions.

Run #6

The sixth run resulted in a chlorine dioxide CT value of 12,722 over a 9-hour period with an

average concentration of 1,413 ppm/hr. The average temperature was 86.3 o

F with an average

RH of 87 percent. All of these values were within the target range. The kill rate for B. subtilis

was 107.8 and the kill rate for B. stearothermophilus was 107

. These results were consistent with

earlier data in which the killing efficiency for B. subtilis was generally an order of magnitude

greater than that achieved for B. stearothermophilus under identical conditions.

This run demonstrates among the highest killing effect for both indicator organisms. It may be

important to note that this run has the highest temperature and relative humidity of all the runs.

Run #7

The seventh and final run resulted in a chlorine dioxide CT value of 14,374 over a 21-hour

period with an average concentration of 684 ppm/hr. The an average temperature was 80.2 oF

with an average RH of 79.3 percent. All of these values were within the target range. The kill

rate for B. subtilis was 107.6 and the kill rate for B. stearothermophilus was 107

. These results

were consistent with earlier data in which the killing efficiency for B. subtilis was generally an

order of magnitude greater than that achieved for B. stearothermophilus under identical

conditions.

This final run was unique in numerous aspects. While it had the second highest overall CT

value, the actual chlorine dioxide concentration within the enclosure was almost one-half of the

concentrations of the previous six runs. In addition, this run had the lowest temperature and

relative humidity values. Even with these lower temperatures and absolute chlorine dioxide

concentrations, the killing efficiency was equivalent to the most effective kills measured in other

runs. Although this is a single experiment, the data are clearly consistent with the concept that it

is the overall chlorine dioxide exposures (concentration times exposure time), not the absolute

ClO2 concentration, that most significantly determines spore killing capability.

Summary of Beltsville Operations

The operational parameters of chlorine dioxide concentration, time of exposure, temperature and

relative humidity chosen for the fumigation runs at Beltsville were all successful in achieving a

minimum of a six log kill of the indicator organisms in a reproducible fashion. Although data

from Washington, DC area and the HSOB indicated the importance of humidity and

temperature, there was not an observable temperature or humidity enhancement in the
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Figure 5.1-9. Bleaching Effect on Photographic

Materials

operational ranges tested at Beltsville. In fact, one of the best kill rates was obtained at the

lowest temperature and relative humidity. This final run also employed a significantly lower

absolute concentration of chlorine dioxide, but with an increased exposure time resulting in an

increased final CT value. These conditions also resulted in an excellent killing efficiency.

Comparisons Between Different Operations

The data presented above represent chlorine dioxide generated via the three methods mentioned

previously. The Johnson and Johnson experiments used gas generated as a result of passing

dilute chlorine gas through a packed bed of flaked NaClO2. The Dugway report used the

electrolysis system, and the Washington DC area EPA data were generated by the solution

method by Sabre Technologies. All of the systems are believed to have generated fairly pure

chlorine dioxide. While all of the systems demonstrate that the chlorine dioxide is capable of

killing bacterial spores, the results do vary. It is possible that this variability is due to

differences in temperature and humidity for the different experimental conditions. Uncertainty

exists because the specific temperature and humidity measurements were not provided. Johnson

and Johnson gave a humidity range of 75-90 percent relative humidity and the Dugway test did

not present temperature data. The data that are presented are very compelling that chlorine

dioxide is an effective agent for killing of spores if used correctly.

Materials Compatibility and Residue

Chlorine is known to react with an extensive variety of compounds, primarily through oxidation

reactions, but it also participates in addition and substitution reactions (EPA, 1981). ClO2 has a

much more limited reactivity towards organics (Rav-Acha, 1984; Masschelein, 1980) and as

such remains available as a biocide even in relatively dirty environments.

The bleaching effect of the gas is

more apparent in synthetic rather

than natural fibers. Most paints are

relatively unaffected by the gas, but

photographic emulsions are

susceptible to bleaching as

illustrated in Figure 5.1-9.

Figure 5.1-9 illustrates the effect of

ClO2 on two separate types of

photograph color images. The

small strip was not exposed to

ClO2, the bottom portions were

exposed to 700 ppm ClO2 for 10

hours at 75 /F at 75 percent relative

humidity. This experiment was

conducted by the U.S. EPA

Emergency Response Team at a

Washington D.C. test trailer in

November 2001.
116

Chlorine dioxide is a strong oxidizer but does not chlorinate organic compounds or amines the

way that chlorine gas does. Chlorine dioxide might penetrate into some materials – such as

porous materials, plastics, and rubbers – resulting in an "off-gassing" period. For example, a

video cassette tape exposed to 500 ppm of chlorine dioxide for eight hours still had a distinctive

odor three weeks after exposure (personal communication: R. Paul Schaudies). An added

advantage of chlorine dioxide over other gas sterilants, such as paraformaldehyde, is that it

leaves no visible residue.

5.1.4.2 Experience with field fumigation of buildings

Experience at the Hart Senate Office Building

On October 15, 2001, an anthrax-containing letter was received in Senator Daschle’s suite in the

Hart Senate Office Building (HSOB). A second such letter, to Senator Leahy, was stopped in

the mail processing system after the Daschle letter was received, and was discovered before it

could be delivered. The letter to Senator Daschle resulted in significant contamination of the

suite itself by anthrax spores. Spores were also drawn into the return ducting of the air handling

system serving the suite (and adjoining suites), and were transported to some other HSOB suites

and common areas by building air movement or occupant activities. Spores were also found in

mail handling facilities in the HSOB and in other nearby Government buildings, resulting from

the processing of the Daschle or Leahy letters, or of other letters that had been crosscontaminated by those two. Collectively, the buildings near Capitol Hill that were impacted by

these two letters are referred to as the Capitol Hill Anthrax Site.

As was to become the pattern in subsequent building anthrax remediations, initial remediation

activities included sealing of the HSOB to prevent further spread of the spores. Environmental

sampling was conducted to define the extent of the contamination, demonstrating high levels of

contamination in multiple areas within the Daschle suite, and lesser levels of contamination in

the return ductwork of the air handling system and in other HSOB suites and common areas. 

Lesser levels of contamination were also found in the affected mail facilities within the Capitol

Hill Anthrax Site.

EPA evaluated a number of alternative decontaminating agents for treatment of the Capiol Hill

Site, including various liquids, foams, gels, and gaseous sterilants. Based upon evaluation by an

interagency committee of advisors, it was decided to use a gaseous sterilant as a central

component of the remediation strategy. For various reasons, including its penetrability, chlorine

dioxide was selected as the gaseous fumigant. Initially, EPA considered fumigation of the entire

HSOB (about 10 million cubic feet of volume). But ultimately, a tiered approach was settled

upon, wherein the initial fumigation would address only the Daschle suite (93,000 ft3

) – the most

highly contaminated area. A decision regarding how to treat any other areas would be made

based upon further environmental sampling, and the experience in the Daschle suite.

Using this approach, it was ultimately decided that – in addition to the Daschle suite itself – the

one other space to be fumigated with ClO2 would be the return ductwork for the air handler

(3,000 ft3). All of the other areas in the HSOB, and other affected buildings, were decontaminated using various topical treatments (in particular, with aqueous ClO2 or sodium hypochlorite).
117

This was the first time that gaseous ClO2 sterilization had been utilized in microbial decontamination of a building.

Prior to the HSOB fumigation, all available experimental data had been obtained under

controlled laboratory conditions in sealed chambers that would fit within a single room of the lab

building. While mathematical calculations appeared to support the feasibility of the ClO2

fumigation approach for the remediation of large buildings, such large-scale field fumigation

using ClO2 had not previously been attempted. As discussed in Section 5.1.4.1, in preparation

for the HSOB remediation, EPA conducted testing in a trailer in Washington, DC, and initiated

controlled laboratory experiments at Dugway Proving Ground, to help define the appropriate

fumigation conditions for this new application.

The field experiments in the Washington, DC, trailer suggested that ClO2 fumigation with a CT

of 9,000 ppm-hr (750 ppm for 12 hr), with a temperature above 75 degrees Fahrenheit, and with

a relative humidity above 75 percent, would provide a six-log kill of Bacillus anthracis spores. 

These conditions were consistent with prior laboratory results.

The first step in the fumigation process was to seal the area to be fumigated, to contain the

fumigant (as well as to prevent the anthrax spores from being transferred into other areas of the

building or outdoors). Comprehensive sealing of Senator Daschle’s suite was achieved using

heavy plastic sheeting around the suite’s interior perimeter, to isolate it from the remainder of

the building. Exterior windows were covered and sealed with light-blocking material, to isolate

the suite from outdoors, and also to prevent UV radiation from entering the space, since sunlight

causes decomposition of ClO2. Other openings through the exterior shell were also sealed.

Relative to the fumigation activities at most of the subsequent remediation sites, the extent of

source reduction in the Daschle suite prior to fumigation was modest. Except in the area

immediately around where the anthrax-containing letter was opened, few building materials or

furnishings were removed. Ceiling tiles, carpeting, furniture, etc., were largely left in place for

decontamination by the fumigant. The exception was that selected valuable artifacts and critical

items were removed for off-site treatment in an ethylene oxide gas sterilization chamber. Also,

paper items were removed from surfaces, drawers, and cabinets, and sent either to an off-site

ethylene oxide sterilization chamber, or to a medical waste incinerator. Topical cleaning of suite

surfaces prior to fumigation – using liquid agents (such as aqueous ClO2 or bleach), or

vacuuming using a high-efficiency particulate air (HEPA) filter – was limited, with the

expectation that the gaseous ClO2 fumigation would adequately sterilize all surfaces.

Chlorine dioxide was generated using the Sabre Oxidation Technologies process. This system

utilizes Equation 5 in Section 5.1.2. Sodium hypochlorite (bleach) solution is first reacted with

HCl to produce chlorine gas (Cl2), followed immediately by reaction of this chlorine with

sodium chlorite solution to produce the ClO2 in aqueous solution. The presence of free chlorine

is minimized or avoided by utilizing excess sodium chlorite.
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The trailer-mounted ClO2 generator and its ancillary equipment was located outside the Hart

Building, at street level below the suite. The aqueous ClO2 solution was pumped up to the suite

through exterior piping, and then passed through air strippers inside the suite to release the

gaseous ClO2 into the sealed space.

Prior to the introduction of ClO2 during fumigation, the RH and temperature in the suite were

first raised to the target values ($75%, $75 o

F) by 12 heaters and humidifiers placed within the

space (Schaudies, 2003). Maintenance of the high relative humidity proved to be an operational

challenge in this initial application of this technology to building fumigation, revealing the

humidification capacity required for this purpose. Following the humidification phase, feed of

aqueous ClO2 solution to the air strippers was initiated (the “conditioning” phase). The “CT

clock” for the fumigation was started after the ClO2 concentration in the space reached the

desired level.

In an effort to achieve uniform mixing of the ClO2, the steam, and the heated air throughout the

suite, nine box-type mixing fans were operated during the fumigation process.

Gas samples for analysis were taken at 16 locations throughout the suite on 10- to 15-minute

intervals, to verify whether ClO2 concentrations were holding at the required level, and whether

the required CT of 9,000 ppm-hr was being achieved. The results showed that the average CT

throughout the suite during the fumigation period exceeded the minimum (averaging 9,600 ppmhr in one part of the suite, and 10,900 ppm-hr in the other part), although there were individual

sampling locations where the CT dropped below the target value (as low as 6,000 ppm-hr at one

location) (Schaudies and Robinson, 2003).

Also, temperature and RH probes were installed at a number of locations throughout the suite to

allow the heaters and humidifiers to be adjusted to maintain the objectives of $75 o

F and $75%

RH. Unfortunately, these probes failed to function during the fumigation due to an electrical

problem, and the temperature and RH measurements had to be made manually by staff inside the

space. The temperatures generally met the target, ranging between 72 and 77 o

F. The RH met

the target in one part of the suite (ranging between 83 and 89% ), but fell below the target in the

other part (ranging between 57 and 75%).

Throughout the fumigation process, EPA’s Environmental Response Team (ERT) monitored the

ambient air in the area around the HSOB using a mobile monitoring van, to confirm that

hazardous amounts of ClO2 gas were not escaping into the environment. A maximum ambient

concentration of 25 ppb was detected over a very short time period; 100 ppb would have been

required to shut down the generator. In addition, stationary air monitors placed in the area

surrounding the HSOB did not measure significant levels of ClO2 during the fumigation.

After the suite had been fumigated, the residual ClO2 gas in the suite was removed by circulating

the suite air through a scrubbing solution. This was accomplished by switching the liquid in the

in-suite air strippers from aqueous ClO2 to the scrubbing solution, thus converting them from

ClO2 emitters into scrubbers. Natural decay of the ClO2 hastened the removal process.
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Following EPA’s issuance of a crisis exemption under FIFRA for the use of gaseous ClO2 in this

application, the fumigation of Senator Daschle’s suite took place over a period ending on

December 2, 2001. The effectiveness of the fumigation was determined in two ways:

 1. Spore strips containing surrogates for the anthrax (Bacillus anthracis) spores. Over

3,000 spore strips containing B. subtilis, B. cereus, B. thuringiensis, and B.

stearothermophilus spores were distributed around the suite – attached to walls, floors,

and furniture, and placed under desks. The spore strips were positioned to verify whether

a sufficient concentration of ClO2 had been maintained for a sufficient time and at a

sufficient relative humidity at each location in the suite to kill the surrogate spores on the

strip.

 2. Environmental sampling to verify whether any surviving B. anthracis spores remained at

the sampling location. Environmental sampling methods included: surface sampling,

using wet wipe and vacuum techniques; and aggressive air sampling, i.e., high-volume

sampling of the suite air after room surfaces had been agitated (blown) in an effort to resuspend any spores that might have been present.

The results from a number of the spore strips were positive, indicating that the concentrationtime-RH-temperature conditions at some locations may not have been sufficient to kill all of the

surrogate spores on the strip. Subsequent testing suggested that some of these apparent positives

may have been due to secondary contamination of the spore strips at various points in the

process: a) during the fumigation, when entries were made into the suite; b) during the postfumigation collection and handling of the strips; and c) during analysis in the laboratory.

The results of the environmental sampling, performed after removal of the spore strips, indicated

a highly significant reduction in contamination of the suite. However, a small percentage of the

samples were positive for the growth of B. anthracis spores. Therefore, surface cleaning with

aqueous chlorine dioxide was then performed in the suite. (As discussed under Section 3.2.4 of

this report, EPA had issued a crisis exemption under FIFRA, allowing the use of aqueous ClO2

against anthrax in this application.)

Following application of the topical aqueous solution, the final environmental samples in the

suite were all negative for growth of anthrax spores.

As indicated previously, the return ducting and filter in the air handling system serving the

Daschle suite had also tested positive for anthrax spores, and was fumigated with ClO2. The

filter was removed. The return ductwork from the Daschle suite – which connected to the

returns from other suites that had not been impacted – was isolated from these other returns. 

Feed lines from the ClO2 gas generator and the steam generator were connected into the return

duct in the suite, and an exhaust fan was connected at the other end of the return ducting (i.e., by

the air handler, several stories above the suite). The ducting was fumigated by using an exhaust

fan to draw ClO2 gas and steam through the contaminated section of return ducting. The ClO2-

containing outlet from the exhaust fan was designed to pass through a scrubber to remove the

ClO2 before being released.
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Chlorine dioxide concentrations were measured at nine sampling locations throughout the

ductwork and air handling system, and temperature and RH probes were installed at seven

locations, to verify whether the concentration and environmental targets were met. Also, a total

of 440 surrogate spore strips were suspended in the air stream at 11 locations within the air

handling system to help assess fumigation efficacy.

Unfortunately, the first attempt at fumigating the return duct was unsuccessful due to difficulties

in maintaining the required fumigation conditions. As a result, some spore strips showed

incomplete kills of the surrogates. Some sections of the ductwork were wiped with aqueous

ClO2 solution, and the ducting was fumigated for a second time on December 28-31, 2001.

Subsequent environmental sampling showed no growth of anthrax spores in any of the samples. 

The HSOB was cleared for re-occupancy and re-opened on January 22, 2002.

Experience at the USPS Brentwood Processing and Distribution Center (Curseen-Morris)

The letters to Senators Daschle and Leahy, containing weapons-grade B. anthracis spores, were

processed through the U. S. Postal Service’s Brentwood Processing and Distribution Center

(P&DC) in Washington, D.C. This facility was the primary Federal mail processing center for

the Washington area. Some of the very fine spores escaped from the envelopes as they passed

through the high-speed sorting machine on Line 17 and other postal equipment. The

contamination was spread in large part through the operation of the mail equipment, and through

the routine use of compressed air to clean the machines of dust and debris. The Brentwood

P&DC was closed on October 22, 2001, after four workers at Brentwood developed inhalational

anthrax. Environmental measurements to determine the extent of the contamination revealed the

greatest number of positive samples at Line 17 and at the two adjacent mail sorting machines,

Lines 16 and 18.

The lessons learned at the HSOB were valuable in guiding the Postal Service’s efforts for

remediation of the Brentwood P&DC.

The building was tightly sealed, to prevent B. anthracis spores from migrating from the facility

prior to remediation. This sealing also served to prevent the large volume of ClO2 gas that

would be inside this building during fumigation from escaping out into the adjoining

neighborhoods. And it served to prevent outside light from entering the building during

fumigation, since ClO2 gas decays quickly in the presence of UV light. In general, plywood or

foam board was attached over exterior windows, doors, and other large openings in the exterior

shell, with caulking and duct tape to ensure a good seal. Unintended openings in the building

shell – e.g., seams between the roofing and the exterior wall – were caulked.

The initial remedial efforts at Brentwood included a series of source reduction steps and spot

decontamination efforts (Princiotta, 2003; Canter, 2004). A significant amount of porous and

non-porous material was treated with bleach, then packaged within the facility and taken off-site

for disposal as infectious waste. Materials thus treated and removed included, for example,

some ceiling tiles; carpeting was generally left in place. Some other materials, such as nonporous postal carts and other rolling stock, were decontaminated with bleach in accordance with
121

the crisis exemption granted by EPA for the use of this aqueous product, and then sent to other

postal facilities for re-use. Surface cleaning of mail sorting machines with bleach was also

conducted.

Following topical bleach treatment of Lines 16, 17, and 18, additional environmental sampling

was performed. This sampling continued to show B. anthracis contamination, but at lesser

levels.

Lines 16, 17, and 18 were then enclosed in a tent of plastic sheeting, and fumigated with gaseous

ClO2 in July 2002. As at HSOB, the selected fumigation conditions inside the tent were

specified as: ClO2 concentration $ 750 ppm; exposure time 12 hours; RH $75%; and

temperature $75 o

F. Surrogate spore strips were used to estimate the efficiency of this

fumigation. Greater than 99% of the spore strips were negative for growth of spores following

the fumigation.

Following this focused treatment of the most contaminated areas, the entire building was

fumigated with a gaseous sterilant. In view of the experience at HSOB, it was again decided to

use ClO2 as the fumigant. However, in this case – rather than treating only selected sections of

the building, as had been possible with Senator Daschle’s suite – the decision was made at

Brentwood to fumigate the entire building (the entire 14 million cubic feet) at one time. This

decision was based on the widespread contamination within the Brentwood facility, and the open

nature of most of the facility.

The Sabre Oxidation Technologies process was again utilized to generate the ClO2 gas for the

fumigation, as it had been at the HSOB. However, because the Brentwood facility had 150 times

the volume of the Daschle suite, the trailer-mounted gas generator used as HSOB was no longer

adequate. A new, larger gas generator was built for this purpose. Also, more substantial

ancillary equipment was required generate the steam needed for humidity control, to provide the

quantities of NaOCl, HCl, and NaClO2 needed to generate the required amount of ClO2, to

distribute the aqueous ClO2 throughout the building and air-strip it inside the building, to provide

the quantities of Na2HSO3 and NaOH needed to generate the Na2SO3 required to scrub the ClO2

gas from the building, and to handle the liquid wastes generated. (The chemistry involved with

the Sabre process was discussed previously in connection with the HSOB remediation.)

As in the case of the HSOB fumigation, the objective was to maintain the building at a ClO2

concentration at 750 ppm or above for 12 hours (for a total CT of at least 9,000 ppm-hr), at a

relative humidity greater than 75% and a temperature of 80 o

F.

At Brentwood, two large exhaust fans (referred to as “negative air units”, or NAUs) were used to

maintain the entire building at negative pressure throughout the fumigation, to prevent escape of

the ClO2 into the ambient air. The objective was to control operation of the NAUs such that the

average pressure across the building shell at the five most positive pressure measurement points

was at least -0.02 inches of water (i.e., that the interior averaged at least 0.02 in. lower in

pressure than the outdoors). The ClO2-containing exhausts from these two NAUs were passed

through HEPA filters, sodium sulfite scrubbers, and carbon sorption beds (which served as a
122

polishing step for ClO2-removal, and as back-up in the event of scrubber failure). The objective

was to reduce the ClO2 concentration in the NAU exhausts to 5 ppm or less.

Modeling calculations showed that – if the NAUs failed to maintain negative pressure in the

building – the resulting leakage of high-ClO2 building air into the ambient could theoretically

result in ambient ClO2 concentrations of 1 ppm half a mile from the site. While this is below the

level considered Immediately Dangerous to Life and Health (5 ppm), it is above the OSHA/

ACGIH 15-minute standard of 0.3 ppm, and underscores the importance of proper functioning of

the NAUs.

In view of these concerns, three tests were conducted on one of the NAUs prior to fumigation. 

The test objectives were to ensure that the sodium sulfite scrubber would function effectively

during the full-scale fumigation, and that the carbon bed alone had the capability to maintain the

exhaust below 5 ppm in the event of a catastrophic failure of the scrubber. Following

improvements to the scrubbers and the carbon beds based upon these tests, the concentration

objectives were successfully achieved.

Following the modifications of the NAU scrubbers and carbon beds, a practice run was

conducted at low ClO2 concentration to confirm that all systems were functioning properly. This

test demonstrated that a several-hundred-ppm ClO2 concentration could be maintained

throughout the building for several hours, that the NAUs could achieve and maintain negative air

pressure inside the building, and that NAU exhaust concentrations could be maintained below 5

ppm. Based upon the results of this low-level run, EPA issued a crisis exemption under FIFRA

to enable the full fumigation to proceed. The fumigation was successfully completed on

December 14-15, 2002.

Throughout the fumigation process, EPA’s Environmental Response Team (ERT) monitored the

ambient air in the area around the HSOB using a mobile monitoring van, sampling for ClO2. 

Measurements were also made at the Brentwood fence-line, and on the building itself. To

protect the adjoining neighborhoods, the generator was to be shut down if ambient levels of ClO2

were at or above 100 ppb for two consecutive 15-minute sampling periods at any of these

ambient monitoring stations. The ambient concentration never reached 100 ppb.

As at HSOB, the success of the fumigation at Brentwood was determined through: 1) surrogate

spore strips throughout the building, to verify that fumigation conditions had in fact been

maintained adequately to kill surrogate spores; and 2) environmental samples taken after

fumigation, including both surface sampling and aggressive air sampling. The U.S. Postal

Service final report indicated that greater than 98% of the spore strips showed complete kills of

the surrogate spores, and that all environmental samples were negative for growth of B.

anthracis spores. Based on these results, the Environmental Clearance Committee

recommended in September 2003 that the facility (now named the Curseen-Morris P&DC) was

safe for re-occupancy.
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Experience at the USPS Hamilton Processing and Distribution Center (Trenton, NJ)

Anthrax-containing letters to the New York Post and to the NBC-TV network offices in New

York City were processed through the Hamilton P&DC on September 18, 2001. The two letters

to Senators Daschle and Leahy were also processed through Hamilton on October 9, 2001. After

five workers at Hamilton were diagnosed with cutaneous or inhalational anthrax, the facility was

closed on October 18, 2001.

Hamilton has a volume of about 6 million cubic feet, less than half the size of the Brentwood

facility. The decision was made that – as with Brentwood – a central component of the Hamilton

remediation would be ClO2 fumigation of the entire building at one time, using the Sabre

Oxidation Technologies process. The fumigation process at Hamilton was postponed until after

the cleanup at Brentwood was completed, so that the ClO2 generators and much of the ancillary

equipment that had been used at Brentwood could be transported to the Hamilton site and used in

this fumigation. A number of refinements were implemented at Hamilton based upon the

Brentwood experience.

The extensive experience at the two fumigations at the HSOB and at Brentwood enabled a more

efficient remediation at Hamilton.

The building was extensively sealed, with the aid of thermal imaging. Exterior doors and

windows were sealed with foam insulation board and layers of plastic sheeting. All openings in

the building shell were sealed with silicone caulk (or expanding foam) and tape, including seams

around the door and window covers, expansion joints in the exterior walls, utility penetrations

through the shell, and gaps where the roof met the walls. Exhaust vents and the building’s sewer

system were sealed. All HVAC penetrations in the shell – including air intake and exhaust

vents – were sealed. The sealing of exterior windows and glass doors serves not only to prevent

spores and ClO2 from escaping into the ambient air, but also prevents UV light from entering the

building and increasing the decay rate of the ClO2.

Significant source reduction activities were conducted at Hamilton prior to fumigation. Critical

items (e.g., cash, mail, key files) were packaged and removed for off-site sterilization. Other

porous materials were removed for disposal, including carpeting, upholstered furniture, ceiling

tiles, some cubicle walls. Such porous materials were treated with modified (pH-neutral) bleach

(sodium hypochlorite) prior to packaging and shipment off-site. Frame walls were left in place.

Many surfaces were cleaned by HEPA vacuuming and/or by wipe-down with modified bleach

solution. Extensive efforts in this regard were made to clean the mail handling equipment that

processed the four anthrax-containing letters. Special focus was placed on those sites within the

building where initial environmental sampling had identified a problem, or where employees had

been stationed who had contracted either cutaneous or inhalational anthrax. To the extent

practical, the HVAC distribution ducting was cleaned with modified bleach, and the existing

HVAC mixing boxes removed and replaced. The removed mixing boxes were cut into pieces,

cleaned with modified bleach on-site, packaged, and shipped for disposal.
124

As in the prior fumigations, the target at Hamilton was to maintain at least 750 ppm ClO2 for a

period of 12 hours (for a CT of 9,000 ppm-hr), at an RH at or above 75%, and a temperature at

or above 75 o

F.

The ClO2 was generated outside the building by the same dual (primary plus back-up) Sabre

reactor system used at Brentwood, reacting aqueous NaOCl with HCl to produce Cl2, followed

instantaneously by reaction of this chlorine with NaClO2 to produce aqueous ClO2. The aqueous

ClO2 was pumped to 12 air strippers distributed inside the building, releasing gaseous ClO2 into

the building air. Relative humidity and temperature were controlled by steam from a boiler

outside the building. During fumigation, the building was held at negative pressure, to avoid

escape of the ClO2 to the outdoors. This negative pressure was maintained by two large exhaust

fans (“negative air units”), which exhausted the ClO2-containing building air through a sodium

sulfite scrubber, with a back-up carbon sorption bed, in order to reduce the stack exhaust

concentration to the 1.8 ppm required by permit.

Between 300 and 400 fans, located throughout the building, were utilized in an effort to ensure

uniform mixing of the ClO2 during fumigation. These included 5,000 acfm tube-axial fans and

2,000-5,000 acfm box fans, as well as the building’s ceiling fans. The building’s internal

HVAC air handlers were also used to assist in the distribution, in that ClO2 released by Sabre’s

emitters was drawn into the air handlers’ return ducting, and distributed throughout the zone

served by each air handler.

The postal machinery inside the building was wired to be operated remotely during the

fumigation process, in an effort to ensure that all components of the equipment were exposed to

the ClO2 gas.

 Consistent with the fumigations at HSOB and Brentwood, this fumigation was conducted in

four steps:

 1) Humidification, in which steam from the exterior boiler (and, as necessary, heat from the

building’s heating system) were used to bring the building up to the required conditions

($ 75% RH, $ 75 o

F). The building had to be held at those conditions throughout for at

least one hour before ClO2 was introduced.

 2) Conditioning, in which aqueous ClO2 introduction into the building began, and the indoor

concentration was raised to the level at which the CT clock would start running. In this

case, the minimum concentration required to start the clock (and to keep it running) was

500 ppm ClO2 at all monitoring sites in the building, although the target concentration

during fumigation was 750 ppm.

 3) Decontamination, in which the ClO2 concentration in the building would be maintained

above the minimum value (and presumably above the target value) – and the RH and

temperature maintained at or above the required values – for the duration necessary to

achieve a total CT of at least 9,000 ppm-hr.
125

 4) Neutralization, in which the ClO2 concentrations in the building would be reduced below

the OSHA 8-hour Permissible Exposure Limit (PEL) of 0.1 ppm following fumigation. 

Neutralization of the ClO2 was achieved by replacing the aqueous ClO2 flows into the air

strippers with sodium sulfite – converting the ClO2 emitters into scrubbers – and by

continued exhausting of the building air through the sodium sulfite scrubbers and carbon

beds associated with the negative air units. Natural decay of the ClO2 also played a role.

Dehumidification is also implemented during the neutralization step, with RH being reduced to

avoid mold growth and other moisture-related problems. Dehumidification to about 50% RH

was achieved by chilling the sodium sulfite solution being delivered to the emitters-turnedscrubbers, so that these scrubbers would also serve as condensers. Further dehumidification to

20% RH – to ensure drying of all interior surfaces over the following two days – was achieved

using silica desiccant dehumidifiers.

Following a series of tests to verify the performance of the negative air units, the building

temperature and RH control system, the building air mixing, and the operability of the total

system at a low ClO2 concentration, EPA issued a crisis exemption for this ClO2 fumigation to

proceed. The four-step fumigation process was conducted beginning on October 24, 2003.

Concentrations of ClO2 were measured using gas samples drawn on an hourly basis from each of

33 sampling locations distributed inside the building. Temperature and RH were monitored

continuously at these same 33 locations, and at some additional locations. In accordance with

the four-step process above, the CT clock for the fumigation was started at 7 pm on October 24,

and continued uninterrupted for 12 hours (until 7 am on October 25), at which time ClO2

generation was stopped. The total average CT exposure throughout the building during that 12-

hour period was about 19,300 ppm-hr (ranging between 15,500 and 21,800 ppm-hr at the various

monitoring locations throughout the building), all well above the 9,000 ppm-hr target.

Throughout the Hamilton fumigation process, EPA’s Environmental Response Team (ERT)

monitored the ambient air in the area around the HSOB using a mobile monitoring van, sampling

for ClO2 and Cl2. Measurements were also made at the fence-line, and on the building itself. 

The ambient concentration never reached the level that would have required generator shutdown. The ClO2 concentration measured by the ERT remote from the building never exceeded

the background level of 3 parts per trillion, well below the level of concern.

As at the other anthrax fumigation sites, the success of the fumigation at Hamilton was

determined through: 1) surrogate spore strips throughout the building, to verify that fumigation

conditions had in fact been maintained adequately to kill surrogate spores; and 2) environmental

samples taken after fumigation, including both surface sampling and aggressive air sampling. 

Slightly more than one percent of the 4,885 individual spore strips were positive for growth. As

a result, additional surface environmental samples were collected at locations where positive

spore strips had been found. All environmental samples were negative for anthrax. Based on the

totality of results, the Environmental Compliance Committee concluded in February 2004 that

the remediation was successful, and recommended that the facility be re-opened.
126

5.1.5 Concerns for the User

Below is a summary of the Occupational Safety and Health Administration’s guidelines for the

use and storage of ClO2. This information was extracted from the following website:

http://www.osha.gov/SLTC/healthguidelines/chlorinedioxide/recognition.html.

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit

(PEL) for chlorine dioxide is 0.1 ppm as an 8-hour time-weighted average (TWA) concentration

(29 CFR 1910.1000, Table Z-1). The National Institute for Occupational Safety and Health

(NIOSH) has established recommended exposure limits (RELs) for chlorine dioxide of 0.1 ppm

as a TWA for up to a 10-hour workday, and a short-term exposure limit (STEL) of 0.3 ppm. The

American Conference of Governmental Industrial Hygienists (ACGIH) has assigned chlorine

dioxide threshold limit values (TLVs) of 0.1 ppm as a TWA for a normal 8-hour workday and a

40-hour workweek, and a short-term exposure limit (STEL) of 0.3 ppm for periods not to exceed

15 minutes. Exposures at the STEL concentration should not be repeated more than four times a

day, and should be separated by intervals of at least 60 minutes.

Exposure to chlorine dioxide can occur through inhalation, ingestion, and contact with the skin

or eyes. To limit or control exposure, the following preventative steps should be taken by the

user: the area of use should be enclosed; local exhaust ventilation should be utilized; and

personal protective equipment should be worn. Chlorine dioxide should be stored in a cool, dry,

well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's

Hazard Communication Standard (29 CFR 1910.1200). Containers of chlorine dioxide should

be protected from physical damage, ignition sources, and light, and should be stored separately

from carbon monoxide, dust, fluoroamines, fluoride, hydrocarbons (e.g., butadiene, ethane,

ethylene, methane, propane), hydrogen, mercury, non-metals (phosphorus, sulfur), phosphorus

pentachloride-chlorine mixture, platinum, potassium hydroxide, water, or steam. To avoid an

explosion hazard, chlorine dioxide should be stored only in diluted forms. Solutions of more

than a 10 percent concentration should not be handled. Empty containers of chlorine dioxide

should be handled appropriately.

The guidelines provide exposure limits and safety considerations for the use of chlorine dioxide

for numerous applications. One might anticipate that, because the gas kills spores, it is also toxic

to humans. It is important to note that the concentrations reported as flammable or explosive are

orders of magnitude higher than those required for sterilization, and are not achieved in normal

operations.

5.1.6 Availability of the Technology for Commercial Applications

There are numerous commercial vendors for the supply of ClO2. Table 5.1-2 presents data for

domestic and foreign manufacturers. While the applications section reflects the information

from the company's website, it is fair to conclude that the chlorine dioxide generated by any of

these systems could conceivably be utilized for decontamination of bacterial spores in buildings

or enclosed spaces. However, some of these technologies have not been tested on a building

scale, and it is possible that practical technical or economic considerations could impact the

applicability of some of these technologies to building applications.
127

Table 5.1-2. Vendors for ClO2

Vendor Name

and Address

Contact Info. 

(Website, Phone, Email)

Products Chlorine Dioxide Generation

Chemistry

CDG140 WebsterStreetBethlehem, PA

(Tel):(888) 610-2562(Fax): (610) 974-9721(Email):info@cdgtechnology.comwww.cdgtechnology.com

Bench-scale and plantscale systems available. 2 NaClO2(solid) + Cl2(gas)6 2 NaCl

+ 2 ClO2 (gas)

DecontaminationWaste waterProcess waterFood processingMedical device ste

DELUWAGmbHJakob-KaiserStrasse 8 D - 47877Willich,Germany

http://www.deluwa.de/engl

isch/frameone.htmwww.deluwa.dewww.chlordioxid.de(Tel) +49 (0) 2154 / 48 6880(Fax) +49 (0) 2154 / 48 6898 (email) info@deluwa.de

DELUDOX chlorinedioxide;Dosing stations;ACODOX disinfectionsystems.

2 NaClO3 + Na2S2O8 6 2 ClO2 + 2

Na2SO4

Reaction conducted in solutionGerman standard EN12671Chemicals used for treatment ofwater intended for humanconsumption - Chlorine dioxide

Destruction of legisystems Disinfection of poProphylaxis of leg(Emergency) disinSterilization of air, systems Disinfection of cotowers Disinfection for thexchangers Sterilization and clinstallations Deodorization and disposal industry Disinfection of slaDisinfection of waDisinfection of CipDisinfection of denDecentralized wasDisinfection of tanDestruction of salmSterilization of conparts (e.g., car parSterilization of clearinsing water Sterilization of conCleaning of emptie
Vendor Name

and Address

Contact Info. 

(Website, Phone, Email)

Products Chlorine Dioxide Generation

Chemistry

128

ERCOWorldwideInformationRequestCoordinator:Sherrie Tack302 The EastMall, Suite200 Toronto,Ontario, CanadaM9B 6C7

http://www.clo2.com

(Tel) 416-239-7111(Fax) 416-239-8091(email) info@clo2.com

Chlorine dioxidegenerators:– ERCO R3– ERCO R3H– ERCO R5– ERCO R7– ERCO R8– ERCO R9– ERCO R10– ERCO R11– ERCO R12– ERCO R13

ERCO R-2 and ERCO R-3processesNaClO3 + NaCl + H2SO4 –> ClO2 +

1/2 Cl2 + Na2SO4 + H2O

ERCO R-5 processNaClO3 + 2HCl –> ClO2 + 1/2 Cl2 +

NaCl + H2O

ERCO R-8 and ERCO R-10processes3 NaClO3 + 2 H2SO4 + 0.85 CH3OH

–> 3 ClO2 + Na3H(SO4)2 + H2O +

0.05 CH3OH + 0.6 CHOOH +

0.2 CO2

ERCO R-11 processNaClO3 + 1/2 H2O2 + H2SO4 –> ClO2+ NaHSO4 + H2O + 1/2 O2

Generators designmills to meet desirthe final bleached 

LenntechWaterTreatment andAirPurificationHolding B.V.Rotterdamseweg 402 M2629 HH DelftTheNetherlands

http://www.lenntech.com/c

hlorine_dioxide.htm(Tel) (+31)(0)15 2610900(Fax) (+31)(0)15 2616289(email) info@lenntech.com

Stabilized chlorinedioxide

Information requested online Hot and cold wate

Vegetables washinBiofilm prevention Cooling towers Scrubbers Potable water Treating iron bacteLegionella
Vendor Name

and Address

Contact Info. 

(Website, Phone, Email)

Products Chlorine Dioxide Generation

Chemistry

129

PureLineTreatmentSystems 25612CommercenterDriveLake Forest,CA 92630

http://www.pureline.com

(Tel) (949) 716-4615(Fax) (949) 716-4645(email)inquiries@pureline.com

Pureline is a watertreatment company withelectrochemical chlorinedioxige generationsystems

Electrochemical processAnode reaction: Cl02- 6 Cl02 + eCathode reactions: 

H2O + e- 6 1/2 H2 + OHNa+ + OH- 6 NaOH

DecontaminationWaste waterProcess waterFood processingMedical device ste

Sabre TechnologiesContact: JohnMason,President2642 MarcoAvenue,Odessa, TX79762

http://www.sabretechnolog

ies.com/(Tel) (209) 482-8199(Fax) (915) 368-4491(email)jmason@sabretechnologies.com(email)gkielman@4clo2.com

Generators– Typical 140– S500-2A– Diklor

Two step solution processHCl(15%) + NaOCl(5-15% avail Cl-)

6 Cl2 + NaOH

2 NaClO2(25%) + Cl2 6 2 NaCl + 2

ClO2 

Undisclosed approach – patentpending

ClO2 fumigationBioterrorism respoWaterWastewaterIndustrial wastewaProcess waterFood processingWell stimulationClO2 evaluations

ScotmasLimitedLindsay HousePoynder PlaceKelso, BordersTD5 7EHScotland

http://www.chlorinedioxide.com

http://www.scotmas.com(Tel) +44 (0)1573 226901(Fax) +44 (0)1573 226026 (email)enquiries@scotmas.com 

Stabilized ClO2 – Biox 

Industrial ClO2 – Cidox 

ClO2 generators – Adox 

Proprietary approach Building services

Water treatmentAgricultureFood hygieneIndustrialHealthcareFormulated produ(Website under co
Vendor Name

and Address

Contact Info. 

(Website, Phone, Email)

Products Chlorine Dioxide Generation

Chemistry

130

Vernagene, Ltd.Units 2 and 3,Waters MeetingBritannia WayBoltonLancashireBL2 2HHUK

http://www.vernagene.com

(Tel) +44 (0) 1204 550820(Fax) +44 (0) 1204 550821(email)enquiries@vernagene.com

Stabilized chlorinedioxide:  – Purogene (small scale) – Harvest Wash (medium/large scale) – Sanogene (large scale)Chlorine dioxide precursor chemicals;Specialist chlorine dioxide dosing systems;Chlorine dioxide generators;Chlorine dioxide monitoring equipment.

Information requested online Disinfection of sys

Food processing aSpeciality applicatPost-harvest citrus washing and sto
131

5.1.7 Cost for generation of ClO2

In an effort to obtain some cost data for the generation of gaseous ClO2, SAIC approached

several vendors in an attempt to get a cost estimate for a chlorine dioxide facility having a

capacity of 30,000 lb ClO2/day. This would have been more than adequate to treat the Hamilton

P&DC, making reasonable assumptions regarding the ClO2 decay rate in the building and the

building exhaust rate. However, the vendors declined to provide costing information, saying that

more information would be required about the envisioned site to permit a meaningful estimate.

5.1.8 Advantages and Disadvantages

All gaseous bioremediation technologies require a gas that is, by definition, reactive. As such,

the material is dangerous to living things. Following are disadvantages for the use of ClO2 in

remediation.

 1. The gas is unstable and must be constantly replaced to attain the target concentration for

the required time.

 2. The gas must be generated onsite, and the equipment required to do this can be

significant.

 3. The killing efficiency decreases significantly at relative humidity levels below 70

percent. Maintenance of humidity is critical.

 4. A large volume of liquid waste materials is generated.

 5. Some reports from field fumigations suggest that some collateral damage may occur to

the surfaces of machinery and electrical systems, resulting from condensation.

The advantages of ClO2 include:

 1. ClO2 is well documented as a disinfectant for spores, vegetative bacteria and viruses.

 2. Rapid natural breakdown of ClO2 eases its removal after application.

 3. The gas is very soluble and stable in water.

 4. The gas is effective on porous and non-porous surfaces and reaches all regions within an

enclosure except for the hardest to reach, isolated areas (e.g., closed employee

lockers).

 5. The gas can be commercially generated by several methods.

 6. The gas leaves no residue.

 7. The gas odor can be detected by humans at a concentration (0.1 ppm) equal to the PEL.

Regarding the potential problem of collateral damage, mentioned above, there have been

undocumented reports from some of the field remediation sites that electrical circuit breakers

needed to be replaced following ClO2 fumigation, potentially due to condensation of moisture

and aqueous ClO2 at the high-humidity conditions. Post-fumigation inspections have indicated

some collateral damage to machinery, equipment, and materials. No electrical shorts have been

observed during fumigation. Collateral damage may be limited in part due to the quick

dehumidification of the buildings following fumigation.
132

5.1.9 Potential Areas for Future Research

Although significant data exist documenting the effectiveness of ClO2 against spores, bacteria,

and viruses, there remain key questions about the combinations of time, concentration,

temperature, and relative humidity for effective killing, about the effectiveness of ClO2 on spores

on different surfaces, about which Bacillus species should be used as surrogates, and about the

performance of ClO2 generation systems in large buildings. To this end there needs to be a

unified method for preparation of bacterial and viral standards for remediation technology

validation. The work at Dugway Proving Ground clearly demonstrates that remediation activity

is spore preparation and surface dependent. The spore preparations dried on filter paper were

significantly more susceptible to the ClO2 than preparations dried on glass slides. Finally,

testing of ClO2 should be conducted on a field scale for some of the commercially available

products to assure that they will perform as intended in large volume structures. 

In order to predict the effectiveness of ClO2 in differing building remediation scenarios, data

need to be generated demonstrating the effectiveness against various agents in differing

circumstances. 

Measurement of ClO2 levels is important for remediation operations. Inexpensive accurate realtime measurements are needed for routine use of this method for building remediation. 

Spectrophotometric methods are available, but the equipment is costly. Air impingers are used

to partition the gas into water for chemical analysis, but this is time consuming. 

A final area that deserves significant attention regarding future research is the use of ClO2 for the

remediation of chemical warfare agents. While it is unlikely that the gas phase of ClO2 will have

an effect on liquefied chemical agents because of limited access of the gas to chemical liquids,

chlorine dioxide in solution may be very effective at degrading chemical warfare agents. The

gas phase may be effective against the chemical warfare vapor. In addition, it is very likely that

ClO2 in water will be effective at oxidizing reactive chemical agents that are harmful but not

considered chemical warfare agents. We are unaware of any testing in this promising research

area.

5.1.10 References for Section 5.1

Aieta and Berg, 1986. Aieta, E. M.; and Berg, J. D. “A Review of Chlorine Dioxide in Drinking

Water Treatment,” J. Amer. Water Works Assoc., 78: 62 (1996).

Alavanja et al., 1980. Alavanja, M.; Goldstein, I.; and Sasser, M. “A Case Control Study of

Gastrointestinal and Urinary Tract Cancer Mortality and Drinking Water Chlorination", in Water

Chlorination: Environmental Impact and Health Effects, Vol. 2, pp. 395. Jolley, R. L., ed. Ann

Arbor Science, Ann Arbor, MI.

Anon, 1977. “Chlorine Dioxide Gains Favor as Effective Sanitizer,” Food Eng., 143 (March

1977).
133

ASTDR, 2004. ToxFAQs for Chlorine Dioxide and Chlorite, Agency for Toxic Substances and

Disease Registry, http://www.atsdr.cdc.gov/tfacts160.html. Accessed November 2004.

Balcer, 1981. Balcer, E. R. “Using Chlorine Dioxide for Slime Control in Alkcaline Paper

Machine Systems,” TAPPI J., 64(8): 91 (1981).

Baran et al., 1973. Baran, W. L.; Dawson, L. E.; and Lechowich, R. V. “Influence of Chlorine

Dioxide Water Treatment on Numbers of Bacteria Associated with Processed Turkey,” Poultry

Sci., 52: 1053 (1973). 

Bernard et al., 1976a. Bernard, M. A.; Snow, W. B.; and Olivieri, V. P. “Chlorine Dioxide

Disinfection Temperature Effects,” J. Appl. Bact., 30: 159 (1976). 

Bernard, 1976b. Bernard, M. A.; Snow, W. B.: Olivieri, V. P.; and Davidson, B. “Kinetics and

Mechanism of Bacterial Disinfection by Chlorine Dioxide,” Appl. Microbiol., 15 (2): 257

(1976). 

Canter, 2004. D. A. Canter, Office of Solid Waste and Emergency Response, U.S.

Environmental Protection Agency, Washington, D.C. Personal communication, August 2004.

Cantor, 1997. Cantor, K. P. “The Epidemiological Approach to the Evaluation of the Health

Effects of Water Chlorination,” presented at Conference on Water Chlorination: Environmental

Impact and Health Effects, Gatlinburg, TN. 

Costilow et al., 1984. Costilow, R. N.; Uebersax, M. A.; and Ward, P. J. “Use of Chlorine

Dioxide for Controlling Microorganisms During the Handling and Storage of Fresh Cucumbers,"

J. Food Sci., 49: 296 (1984).

Davy, 1811. Davy, H. Phil. Trans., 101:155 (1811). 

Du et al., 2002. Du, Jinhua; Han, Y.; and Linton, R. H. “Chlorine Dioxide Gas Kills Dangerous

Biological Contaminants,” Department of Food Science, Purdue University, September 2002. 

Available at: http://news.uns.purdue.edu/UNS/html4ever/020912.Linton.chlorinediox.html. 

Accessed November 2004.

Emsweiler et al., 1976. Emsweiler, B. S.; Kotula, A. W.; and Rough, D. K. “Bacterial

Effectiveness of Three Chlorine Sources Used in Beef Carcass Washing,” J. Anim. Sci., 42: 1445

(1976).

EPA, 2004. Pesticides: Topical & Chemical Fact Sheets -- Chlorine Dioxide. U.S.

Environmental Protection Agency. Available at:

http://www.epa.gov/pesticides/factsheets/chemicals/chlorinedioxidefactsheet.htm. Accessed

November 2004.
134

EPA, 1999. "Chapter 4: Chlorine Dioxide," in Guidance Manual - Alternative Disinfectants and

Oxidants. EPA-815-R-99-014. U.S. Environmental Protection Agency, Office of Water,

Washington, D.C. 

EPA, 1981. Treatment Techniques for Controlling Trihalomethanes in Drinking Water,

EPA/600/2-81-156. U.S. Environmental Protection Agency, Cincinnati, OH. 

EPA, 1979. Effectiveness of Chlorine Dioxide as a Wastewater Disinfectant, in Progress in

Wastewater Disinfection Technology, EPA-600/9-79-018. U.S. Environmental Protection

Agency, Cincinnati, OH. 

ERCO, 2004. “Water Treatment with ClO2.” Available at:

www.clo2.com/wtupgrade/treatment.html. Accessed November 2004.

Freymark and Rauh, 1978. Freymark, S. G.; and Rauh, J. S. “Selective Oxidation of Industrial

Wastewater Contaminants by Chlorine Dioxide,” Proceedings: Mid. Atl. Ind. Waste Conf., Vol.

10, page 120.

Kirk-Othmer, 1993. Encyclopedia of Chemical Technology, Fourth Edition, Volume 5,

“Chlorine Oxygen Acids and Salts (ClO2, HClO2).” Pages 976-979.

Lillard, 1979. Lillard, H. S. “Levels of Chlorine and Chlorine Dioxide of Equivalent

Bactericidal Effect in Poultry Processing Water,” J. Food Sci., 44: 1594 (1979).

Masschelein, 1980. Masschelein, W. J. “The State of Art in the Use of Chlorine Dioxide and

Ozone in the Treatment of Water,” Water SA, 6(3): 116-129 (1980).

McCarthy, 1945. McCarthy, J. A. “Chlorine Dioxide for the Treatment of Water Supplies," J.

NEWWA, 59: 252 (1945). 

Oliver et al., 1989. Oliver, S. P.; King, S. H.; Torre, P. M.; Shull, E. P.; Dowlen, H. H.; Lewis,

M. J.; and Sordillo, L. M. “Prevention of Bovine Mastitis by a Postmilking Teat Disinfectant

Containing Chlorous Acid and Chlorine Dioxide in a Soluble Polymer Gel,” J. Dairy Sci., 72:

3091 (1989). 

Page et al., 1976. Page, T.; Harris, R. H.; and Epstein, S. S. “Drinking Water and Cancer

Mortality in Louisiana,” Science, 193: 55 (1976).

Princiotta, 2003. F. T. Princiotta and G. B. Martin, “Observations on Engineering Aspects of the

Brentwood Postal Facility Fumigation,” presented at the First World Conference on Risk,

Brussels, Belgium, June 2003.

Rauh, 1979. Rauh, J. S. “Disinfection and Oxidation of Wastes by Chlorine Dioxide,” J.

Environ. Sci., 22(2): 42 (1979).
135

Rav-Acha, 1984. Rav-Acha, C. “The Reactions of Chlorine Dioxide with Aquatic Organic

Materials and Their Health Effects,” Water Res., 18(11): 84 (1984).

Ridenour and Armbruster, 1949. Ridenour, G. M.; and Armbruster, E. H. “Bactericidal Effects

of Chlorine Dioxide,” J. Amer. Water Works Assoc., 41: 537 (1949). 

Roe, 1976. Roe, F. J. C. “Preliminary Report of Long-Term Tests of Chloroform in Rats, Mice

and Dogs,” unpublished Report. Cited in: Ozone, Chlorine Dioxide and Chloramines as

Alternatives to Chlorine for Disinfection of Drinking Water. Water Supply Research, U.S.

Environmental Protection Agency, Office of Research and Development, Cincinnati, OH. 

Schaudies and Robinson, 2003. Schaudies, R. P.; and Robinson, D. A. “Analysis of Chlorine

Dioxide Remediation of Washington, DC, Bacillus anthracis Contamination,” report to the U.S.

Environmental Protection Agency under Contract No. GS-23F-8006H, 2003.

Synan et al., 1975. Synan, J. F.; MacMahon, J. D.; and Vincent, G. P. “Chlorine Dioxide, A

Development in the Treatment of Potable Water," Water Wks. and Sew., 91: 566 (1975).

Thiessen et al., 1984. Thiessen, G. P.; Usbome, W. R.; and Orr, H. L. “The Efficacy of Chlorine

Dioxide in Controlling Salmondla Contamination and Its Effect on Product Quality of Chicken

Broiler Carcasses,” Poultry Sci., 63: 647 (1984). 

West Dugway Test Center, 2002. “Abbreviated Test Report for the Validation of Chlorine

Dioxide Decontamination,” Test Project No. 8-CO-210-000-084, WDTC Document No. WDTCTR-02-059. (Note: Contents of the cited report appearing in the current document are used by

permission. Requests for the entire document should be referred to the U.S. EPA, Region 8,

8EPR-ER, 999 18th Street, Suite 300, Denver, CO 80202.)
136

Figure 5.2-1. Chemical Reactions to Generate and

Remove Hydrogen Peroxide from the Air

(Source: STERIS Corporation)

5.2 Hydrogen Peroxide Vapor

The use of aqueous hydrogen peroxide as a decontaminant has a long history (see Section 3.3 of

this report). One of the earliest published records for use of aqueous H2O2 is from 1883, when

hydrogen peroxide was used as a bactericide to preserve milk (Schrodt, 1883). A comprehensive

review of the early uses of aqueous hydrogen peroxide as a disinfectant was published in 1972

(von Bockleman and von Bockleman, 1972). In 1989, the U.S. Environmental Protection

Agency (EPA, 2004a) approved the use of vapor-phase hydrogen peroxide as a sterilization

process.

5.2.1 Description of the Technology Alternative

A number of hydrogen peroxide vapor generation systems are commercially available for smallscale chamber sterilization of, for example, pharmaceutical equipment. Several of these have

been adapted for potential use in the fumigation of larger volumes, applicable to buildings.

In all cases, the hydrogen peroxide vapor is generated from a concentrated aqueous solution of

hydrogen peroxide ($30% H2O2). The vapor may be generated by controlled heating of the

liquid, in a manner that reduces

decomposition of the H2O2. Other

methods, such as heated aerosolizers,

have been considered. Like other

oxidizing fumigants, the peroxide

decays with time – at a rate even faster

than ClO2 – and it is thus necessary to

continuously supply fresh peroxide into

the space at a rate sufficient to maintain

the desired concentration. As

discussed later, typical H2O2 vapor

concentrations (e.g., 200 ppm, or about

0.3 mg/L) might require perhaps 2 to 6

hours of contact time to destroy anthrax

spores, depending on the substrate. At

the end of the operational cycle, the

H2O2 generator is turned off, and hydrogen peroxide vapor is withdrawn from the space and

passed over a catalyst (complementing the natural decay) to convert it into water and oxygen,

thus leaving no toxic residue (Lauderback et al., 2002). Figure 5.2-1 shows a schematic of the process.

Relative humidity is an important parameter in determining the performance of hydrogen

peroxide vapor, although the optimal RH level varies with the specific H2O2 process. The

STERIS process, discussed below, maintains a low humidity in the space (below 40% RH at the

start of fumigation), in an effort to keep the peroxide in the vapor phase for improved penetration

of substrate surfaces. By comparison, the BIOQUELL process permits higher RH values,

attempting to achieve “micro-condensation” of a thin film of peroxide over the surface to be

decontaminated.

5.2.2 Technical Maturity
137

Figure 5.2-3. The

STERIS VHP 1000

Vaporized Hydrogen

Peroxide system.

Hydrogen peroxide vapor is well documented in

the literature as an effective sterilizer of viruses,

fungi, bacteria, and spores in controlled

laboratory environments (Block, 2001; Klapes

and Vesley, 1990; Kokubo et al., 1998). It has

been registered by EPA for use as an

antimicrobial pesticide for sterilization of sealed

enclosures such as isolators, workstations, and

pass-through rooms in commercial, institutional,

and industrial settings (EPA, 2004a). The

process is commercialized and hydrogen

peroxide vapor generation systems are offered as

turnkey operations. Hydrogen peroxide vapor is

generated from concentrated aqueous hydrogen peroxide solution (Lauderback et al., 2002). 

Figures 5.2-2 and 5.2-3 show hydrogen peroxide vapor generation

systems that are commercially available from BIOQUELL and

STERIS.

The BIOQUELL Clarus C was designed for use in the pharmaceutical

industry for the sterilization of filling lines, isolators, and clean

rooms. This unit is being considered for adaptation to address

building fumigation applications. The smaller unit, Clarus L, is

designed for smaller applications such as incubators and equipment

sterilization. The hydrogen peroxide product used in BIOQUELL’s

Clarus C and Clarus L systems is not registered with EPA under

FIFRA.

STERIS Corporation is another manufacturer of hydrogen peroxide

vapor equipment (referred to as Vaporized Hydrogen Peroxide®, or

VHP). Their larger unit, the VHP 1000 (shown in Figure 5.2-3), has

been used for decontamination of chambers and enclosed areas for ten years and is applicable for

rooms up to 6,000 ft3

 in size. The STERIS hydrogen peroxide product has been registered by

EPA under FIFRA. In more recent operations, multiple units were combined in a single

operation to remediate significantly larger rooms. Scaled-up versions of the VHP 1000 have

recently been tested by STERIS, with multiple units being combined to treat volumes up to

200,000 ft3

 in actual applications (SAIC, 2003). This represents a significant enhancement in

capability. 

The STERIS Corporation was contracted to conduct fumigation of the two U.S. Government

mail facilities that were contaminated with Bacillus anthracis spores via the mail system: the

General Services Administration’s Building 410 in Washington, D.C. and the U.S. State

Department Mail Facility in Sterling, Virginia, (Loudoun County, 2004). The buildings were

sectioned into smaller areas (approximately 100,000 to 200,000 ft3 each) and fumigated with the

hydrogen peroxide vapor. The experience at the State Department facility is discussed further in

Section 5.2.4 of this report.

Figure 5.2-2. The BIOQUELL Clarus C

and Claris L Units for hydrogen peroxide

vapor generation.
138

5.2.3 Applications for Hydrogen Peroxide Vapor

Hydrogen peroxide is a strong oxidizing agent with a wide variety of applications. As a dilute

aqueous solution (3 percent) it is sold for home use for disinfecting minor cuts and scrapes. 

More concentrated (10 percent) solutions are used for home hair bleaching treatments. See

Section 3.3. The strong oxidizing potential of hydrogen peroxide is highlighted by the

incorporation of hydrogen peroxide in ecologically friendly rocket propellants (Lauderback et

al., 2002). 

Aqueous hydrogen peroxide has been in use for over one hundred years for its ability to kill

bacteria (Schrodt, 1883). Specific aqueous H2O2 products (including hydrogen peroxide and

peroxyacetic acid mixtures) have been registered for indoor use on hard surfaces (e.g., in food

establishments, medical facilities, and home bathrooms) since as early as 1977, and have been

granted crisis exemptions by EPA for used on hard surfaces for destruction of anthrax spores

(EPA, 2004b). Hydrogen peroxide in the vapor form is registered as a pesticide by EPA for use

in killing bacterial spores on environmental surfaces within enclosed areas in commercial,

institutional, and industrial settings (EPA, 2004a). More recently, H2O2 vapor has been granted

crisis exemptions for treatment of anthrax spores specifically in the fumigations of GSA

Building 410 and the State Department mail annex, mentioned above.

Vaporized hydrogen peroxide generators generally use a 35 percent aqueous hydrogen peroxide

solution (Lauderback et al., 2002). The aqueous hydrogen peroxide is vaporized at temperatures

of 70-140 °C. In this vaporized form, hydrogen peroxide has been reported to inactivate

pathogenic bacteria, yeast, and bacterial spores. The rate of activity of peroxide is sharply

increased by heat, ultraviolet light, and ultrasonic energy. There have been promising results

from experiments using peroxide vapor for space decontamination of rooms and biologic safety

cabinets (Kirk-Othmer, 1993). 

Hydrogen peroxide vapor is registered as an antimicrobial pesticide for use in commercial,

institutional, and industrial settings, for the decontamination or sterilization of sealed enclosures

including scientific workstations, isolators, pass-through rooms, and medical and diagnostic

devices (EPA, 2004a). Hydrogen peroxide vapor decontamination technology has been used in

the pharmaceutical industry for over ten years. More than 700 hydrogen peroxide vapor systems

are used in this industry worldwide, and they have proven to be effective against a variety of

microorganisms (STERIS, 2004). 

Vaporized hydrogen peroxide is also used in plasma sterilizers. These commercially available

sterilizers use hydrogen peroxide and a vacuum as in the standard hydrogen peroxide vapor

generators, but also use low pressure plasma. The plasma induces free radicals and ions,

enhancing the hydrogen peroxide vapor’s effectiveness at killing microbes. Experiments using

hydrogen peroxide vapor conducted with and without plasma suggest that the addition of plasma

to the equation results in a better, faster decontamination (Sias, 2003). This decontamination

technology is used for sterilizing surgical instruments. A patent exists for the use of peroxide

vapor and a radio frequency energy generated plasma which releases free radicals, ions, excited

atoms, and excited molecules in a sterilizing chamber (U.S. Pat. 4,643,876, 1987, P.T. Jacobs

and S.M. Lin) (Kirk-Othmer, 1993). Yet another variation of hydrogen peroxide vapor

decontamination technology exists, Binary Ionization Technology (BIT). BIT also uses
139

hydrogen peroxide and plasma, but it does not require a vacuum environment or containment

within a chamber (Sias, 2003).

Although vaporized hydrogen peroxide and hydrogen peroxide plasma technologies have proven

to be effective decontamination methods, they did not have widespread acceptance as of 1996. 

Historically, steam, ethylene oxide, and dry heat have been the preferred methods of sterilization

of biomedical devices (Kirk-Othmer, 1997).

5.2.4 Evaluation of Available Data

5.2.4.1 Data from laboratory testing

The efficacy of a chemical as a sporicide is expressed in terms of log kills and D-Values. A one

log kill represents 90 percent killing efficiency. A six log kill, required for sterilization is a

99.9999 percent killing efficiency. A D-value is the contact time required for a one log kill. In a

1991 published report the D-values of liquid and hydrogen peroxide vapor were compared using

three different bacterial spore types. As shown in Table 5.2-1, the concentration of hydrogen

peroxide in water is over 200-fold greater than the concentration required in the vapor-phase to

achieve similar microbial activity (Block, 2001).

Table 5.2-1. Effectiveness of Hydrogen Peroxide Liquid and Vapor on Spores 

Test Organism

(spores)

D-value (time to kill one log of test organism in minutes)

Liquid

H2O2 Concentration 370 mg/L

Temp 24-25 Celsius

Vapor

H2O2 Concentration 1-2 mg/L

Temp 24-25 Celsius

B. stearothermophilus 1.5 1-2

B. subtilis 2.0-7.3 0.5-1

C sporogenes 0.8 0.5-1

STERIS Corporation provided the data shown in Figure 5.2-4.

The D-values (time required to kill 90 percent of the initial population) for a variety of bacterial

spores were determined with hydrogen peroxide vapor. Spore populations of 106

 were deposited

onto 316 stainless steel coupons. The contaminated coupons were exposed to Vaporized

Hydrogen Peroxide at a concentration of 1,370 ppm at approximately 30-37 oC. The

thermophilic Geobacillus stearothermophilus, which is used on many commercial biological

indicators, exhibited the greatest resistance to the process as shown in Table 5.2-2.
140

 Figure 5.2-4. Hydrogen Peroxide Vapor Concentration versus D-value

Table 5.2-2. D-Values of bacterial spores exposed to 1,370 ppm hydrogen peroxide

vapor at 30-37 o

C

Organism D-Value (seconds)

Geobacillus stearothermophilus 42.3

Bacillus subtilis 18.7

Clostridium sporogenes 15.6

Bacillus circulans 14.4

Bacillus cereus 9.9

The performance of hydrogen peroxide vapor is sensitive to temperature and humidity

conditions. Hydrogen peroxide vapor was applied at different temperatures, and D-values were

determined. As seen in Table 5.2-3, a higher equilibrium concentration of the hydrogen

peroxide vapor was achieved at higher temperatures since the air was less saturated with water
141

vapor. The process was more effective at the higher temperatures due to the increased

concentration, as well as the faster reaction rates of hydrogen peroxide vapor reacting with the

target cell constituents.

Table 5.2-3. Hydrogen peroxide vapor efficacy at various temperatures against

Geobacillus stearothermophilus spores

Temperature (oC) Hydrogen Peroxide Vapor

Concentration (ppm)

Typical D-Value

4 350 8 – 12 minutes

25 700 – 1500 1 – 2 minutes

37 2000 - 3000 30 – 60 seconds

55 > 7000 One second

In pharmaceutical manufacturing, the performance of hydrogen peroxide vapor is routinely

monitored by the use of biological indicators (BIs). The BIs are either strips of polymeric nonwoven fabric or stainless steel coupons inoculated with spores of Geobacillus

stearothermophilus or other appropriate indicator microorganism. A successful decontamination

cycle is determined by complete inactivation (sterilization) of the biological indicator. 

Geobacillus stearothermophilus spores have been identified as the most resistant organism to the

hydrogen peroxide vapor process (Rickloff and Orelski, 1989). 

In response to the anthrax containing letters delivered to Florida, New York, and Washington,

D.C., the U.S. EPA in Denver Colorado contracted the West Desert Test Facility at Dugway

Proving Ground to test the effects of ClO2 and hydrogen peroxide vapor on a variety of dried

Bacillus spores:

• BAA – Bacillus anthracis var. ames,

• BAV – Bacillus anthracis var. vollum,

• BAS – Bacillus anthracis var. sterne,

• BGN – Bacillus subtilis var. niger,

• BT – Bacillus thuringiensis, and

• BST – Bacillus stearothermophilus.

The ClO2 data from this testing were discussed in Section 5.4.1.1. The data obtained from the

one trial with H2O2 vapor are discussed and illustrated below, excerpted from the study report

(West Dugway Test Center, 2002).

Spores from three strains of Bacillus anthracis (BA) and three BA simulants were applied as a

liquid slurry and dried on either glass cover slips (all six organisms) or porous filter paper (BAA

and BAV only), and were exposed to hydrogen peroxide vapor in a chamber under controlled

conditions for 12 hours. The Dugway team did not control for temperature; discussions with the

team indicated that they operated at ambient temperatures (70-75 /F).

During the course of the 12-hour run, triplicate slides were removed from the sterilization

chamber at specific time intervals, and cultured to determine presence of viable spores.
142

Hydrogen peroxide vapor was used during Trial 6. The vapor was generated using a STERIS

VHP1000 unit in accordance with the manufacturer’s instructions (STERIS, 1996), heating 30 to

35 percent aqueous H2O2 to form the vapor. The VHP1000 unit operates on a four-phase cycle. 

In the first phase – which occurred prior to the introduction of gas into the Dugway chamber –

the chamber was dehumidified utilizing a dehumidifier incorporated into the VHP1000 unit. 

Dehumidification is important in the VHP process, to reduce condensation of aqueous H2O2. 

Dehumidification was followed by the second, conditioning phase In this phase, the generator

introduced hydrogen peroxide vapor into the chamber at a rapid rate, to reach the desired

chamber operating concentration as quickly as possible. After the desired concentration was

achieved, the VHP1000 unit switched to the third, or fumigation, phase, reducing the hydrogen

peroxide vapor generation rate to the level required to maintain the desired concentration at

steady state for 12 hours. (This steady-state peroxide concentration was determined by the

vendor’s settings on the VHP1000 unit, and was not measured during this study.) The fourth and

last phase of operation was the aeration phase, in which the residual hydrogen peroxide vapor in

the chamber was removed so that the chamber could be opened without causing harm to

personnel.

The data obtained for this experiment is illustrated in Figure 5.2-5, as excerpted from the EPA

report. These results show that – at the potentially high gaseous H2O2 concentrations in the

chamber – all of the B. anthracis surrogates (BGN, BT, BST, and non-virulent B. anthracis v.

sterne) had been completely killed on the glass cover slips within 1 hour (a 6- to 8-log reduction

in spores). The virulent B. anthracis v. ames strain (BAA) experienced a 6-log kill in 1 hour,

and complete (7-log) kill in 2 hours. B. anthracis v. vollum (BAV) proved to be the most

resistant to H2O2 vapor, requiring 4 hours to sustain a 6-log kill, and 6 hours to experience total

(8-log) kill.

Hydrogen peroxide vapor does interact with many materials, decaying in contact with the

surface, but it does not appear to be corrosive. Discoloration of dyes can occur and interactions

with nylon are not favorable. It has been reported that nylon and other porous surfaces interact

with the hydrogen peroxide and degrade it, thereby making it inactive. In a personal

communication with STERIS representatives during the anthrax response in Washington, D.C.,

they reported that the gas was inactivated by celluloid compounds. This includes paper and

paper products. In a more recent communication with Dr. Peter Burke of STERIS, he claimed to

have more recent data indicating less rapid decay of the vapor against porous surfaces (SAIC,

2003).

Research is underway through a work-in-kind cooperative research and development agreement

between Lawrence Livermore National Laboratory and STERIS Corporation to evaluate the use

of heating, ventilation, and air conditioning (HVAC) systems as a means to convey Hydrogen

peroxide vapor into building environments. The experiments are evaluating the delivery of VHP

through the HVAC system, and quantifying the spore kill by culturing indicator strips (Carlson

and Raber, undated).
143

Figure 5.2-5. Log of Colony Forming Units (cfus) Remaining at Each Time Point for Trial

6; Laboratory Validation of Hydrogen Peroxide Decontamination

NOTE: BAA – Bacillus anthracis var. ames, BAV – Bacillus anthracis var. vollum, BAS – Bacillus anthracis var.

sterne, BGN – Bacillus subtilis var. niger, BT – Bacillus thuringiensis, BST – Bacillus stearothermophilus.

5.2.4.2 Experience with field fumigation of buildings

Experience at the U.S. Department of State Mail Annex (SA-32), Sterling, VA

This State Department mail processing facility (SA-32) in Sterling, VA, was contaminated with

B. anthracis spores in October 2001, possibly because the anthrax-containing letter addressed to

Senator Leahy may have been mis-directed to SA-32 prior to being returned to the Brentwood

P&DC (discussed in Section 5.1.4.2). SA-32 contains 1.4 million cubic feet of volume, making

it about one-quarter the size of the USPS Hamilton P&DC, and about one-tenth the size of the

Brentwood P&DC.

As with all of the buildings impacted by the 2001 anthrax mail attack, the initial step in the

remediation process for SA-32 was environmental sampling (swab sampling and vacuum sock

sampling) to characterize the extent of the contamination. Four such sampling events took place

in October and November 2001.
144

With confirmation that the facility was contaminated, a significant effort was undertaken to seal

the building, to prevent release of the spores to the outdoor environment and, ultimately, to

prevent escape of the as-yet unselected fumigant. All exterior doors (including loading dock

doors), windows, and vents were sealed with caulked polyethylene sheeting, and covered with

plywood to prevent puncture of the sheeting. The rooftop HVAC units that served the building

were all removed (after having been cleaned from inside the building), and the resulting

openings in the roof were sealed in the manner described above. All plumbing fixtures inside

the building were removed, and the water lines and plumbing vents capped. Following

subsequent testing for leak-tightness, additional sealing was also performed, including caulking

around the joint where the exterior walls meet the roof.

In addition, five exhaust fans (“negative air machines”, or NAMs) were installed on the building

– exhausting through HEPA filters, to capture any anthrax spores that could be in the exhaust –

to maintain the building under negative pressure throughout this entire process. This was

intended to prevent any spores inside the building from escaping into the ambient air.

Critical and salvageable items were decontaminated by several approaches for re-use. Over

70,000 lb of flat mail was treated by irradiation. Bulk parcels were cleaned by HEPA

vacuuming, then tested for B. anthracis to verify the effectiveness of treatment. Personal and

office items, including file cabinets and document storage units, were treated off-site using

ethylene oxide sterilization. Over 46,000 diplomatic mail pouches were sterilized using

paraformaldehyde, using pre-constructed chambers set up in the SA-32 building for this purpose.

All interior finish and all postal equipment was removed from the building, reflecting the most

substantial source reduction effort of any of the remedial actions taken in response to the anthrax

mail attack. All interior frame walls, ceilings, carpeting, furnishings, etc., were removed, broken

down, treated with amended bleach (pH-adjusted sodium hypochlorite with acetic acid) or with

an aqueous hydrogen peroxide/peroxyacetic acid product (Spor-Klenz®), packaged, and sent for

destruction at a permitted medical waste facility. Large metal items, such as the mail handling

equipment, were washed with soap and water, broken down, and placed in large containers,

which were shrink-wrapped in plastic. The exterior of the shink-wrap was cleaned with SporKlenz, the containers were shipped for off-site ethylene oxide treatment, and the resulting

sterilized metal was recycled as scrap.

Following the removal of this interior finish and equipment, only the building shell remained –

the exterior walls (and a few interior structural walls), the slab, the metal sheeting supporting the

flat built-up roof overhead, and the metal roof trusses, along with the electrical system. All of

these remaining interior surfaces were HEPA vacuumed, and washed with soap and water. In

six areas known to have been contaminated by anthrax, based on the pre-remediation

environmental sampling, the surfaces were also wiped down with the amended bleach or SporKlenz.

The original intention had been to fumigate the entire facility with paraformaldehyde. However,

following evaluation of alternative building remediation approaches, the State Department

selected gaseous H2O2 as the fumigant to be employed, using the STERIS Vaporized Hydrogen

Peroxide process.
145

For the fumigation utilizing the STERIS VHP gaseous H2O2 process, the cleaned and basically

empty 1,400,000 ft3 building was physically subdivided into zones using plastic sheeting. 

Initially, there were seven zones, each approximately 200,000 ft3 in volume. These zones would

be fumigated one at a time. The decision was made to subdivide the building, in part, in order to

reduce the H2O2 generation capacity that would have been required on-site were the entire

building volume to be fumigated at once. In addition, the VHP process had not previously been

used to treat volumes of this size, except at GSA Building 410, which also had been subdivided

into 200,000 ft3

 zones. This subdivision into zones was achieved using polyethylene sheeting

that extended the entire width of the building, anchored to the floor slab, to the metal underside

of the roof, and to the front and rear walls.

The target fumigation conditions were that the vaporized H2O2 concentration in each zone would

have to be held at or above 0.3 mg/L (216 ppm) for 4 hours; the temperature would have to be

$70 oF; and the “saturation level” would have to be #80%, to avoid condensation. The

saturation level is defined as the concentration of water vapor plus H2O2, expressed as a

percentage of the dew point concentration of these two compounds in combination at the

prevailing temperature. It is noted that this peroxide concentration and exposure time (a total

CT of 860 ppm-hr) are much lower than the values specified for ClO2 fumigation, discussed in

Section 5.1.4.2 (750 ppm for 12 hr, or 9,000 ppm-hr), reflecting a higher reactivity of H2O2.

Sensor bundles were placed at six locations within each zone during its fumigation (with H2O2

monitors at two additional locations), to continuously monitor the concentrations of H2O2 and

water vapor, and the temperature, to ensure that the target process conditions were achieved. 

Among the buildings remediated following the 2001 anthrax mail attack, this was the only

fumigation in which real-time monitoring of fumigant concentration occurred. In addition,

chemical indicators (strips that changed color when exposed to a certain H2O2 CT) and biological

indicators (stainless steel spore strips containing 106 spores of an anthrax surrogate, Geobacillus

stearothermophilus) were distributed throughout each zone, with approximately one of each type

of strip per 100 ft2

 of zone floor area. The chemical and biological indicators were co-located. 

Fumigation of a given zone was judged to be complete when the target fumigation conditions

had be satisfied in that zone, when all chemical indicators had changed color, and when all

biological indicators were negative for growth of the indicator spores when cultured following

fumigation.

The STERIS H2O2 generation system was installed outdoors, near one corner of the SA-32

facility. This system consisted of multiple (four to six) generators – each representing a

specially-designed adaptation of the VHP 1000 unit pictured in Figure 5.2-3 above – having a

total combined capacity initially deemed to be more than adequate to treat each of the seven

200,000 ft3

 zones. These generators produced gaseous H2O2 by vaporizing an aqueous 35%

H2O2 feed solution.

In commercial practice, in the fumigation of small volumes, the VHP units automatically cycle

the treated volume through four phases. These four phases include: dehumidification, in which

the RH of the space is reduced to 40% or less; conditioning, in which the introduction of H2O2

vapor at high concentration is initiated, to bring the space up to the target fumigation

concentration as quickly as possible (while maintaining the saturation level at 80% or less);

decontamination, in which the space is maintained at or above the target concentration, at or
146

above the target temperature, and below the target saturation for the specified time; and finally

aeration, in which the air within the space is cycled through a catalyst bed to destroy the residual

H2O2, reducing concentrations to a safe level. (The H2O2 concentration considered Immediately

Dangerous to Life and Health is 75 ppm – less severe than the 5 ppm for ClO2 – and, commonly,

the objective is to reduce the concentration below 1 ppm, the OSHA Permissible Exposure

Limit, during the aeration phase.)

The specially-designed large-volume VHP system installed at SA-32 was configured to put the

200,000 ft3

 zone through this same cycle. A blower near the generators recirculated the zone air. 

The galvanized metal ductwork system associated with this blower was manifolded such that it

could withdraw air from, and supply air to, any one of the original seven zones, as controlled by

dampers within the ductwork. Air would be supplied to one end of the selected zone, and

withdrawn from the other end of that zone. The modified VHP generators introduced vaporized

H2O2 into the supply side of this blower during the conditioning and decontamination phases for

the selected zone.

A regenerative desiccator was incorporated into this recirculation loop. During the

dehumidification phase, zone air was circulated through this dryer without the VHP generators

operating, in order to reduce the relative humidity in the zone to 40% or less before conditioning

began. During conditioning and decontamination, the dessicator served to reduce the observed

increase in the zone’s RH, helping prevent the zone’s calculated saturation level from exceeding

80%.

The return air drawn out of the zone was passed through a HEPA filter (to remove any spores or

dust) and a catalyst bed (to destroy the H2O2 in the extracted air stream) before entering the dryer

and blower. The residual H2O2 was destroyed during conditioning and decontamination to

facilitate control of the process. During the aeration phase, recirculation of zone air through this

catalyst bed helped reduce concentrations below 1 ppm H2O2.

During the fumigation of each zone, at least 20 mixing fans were in operation within that zone,

in an effort to distribute the H2O2 uniformly throughout the zone.

While the fumigation of a given zone was underway, a 5,000 cfm exhaust fan drew air from all

of the zones not being fumigated, keeping the remainder of the building at negative pressure

relative to the fumigated zone and relative to outdoors. The H2O2-containing exhaust from this

fan was passed through a catalyst bed, to reduce the H2O2 concentration to a very low level prior

to release to the atmosphere. The building was maintained under negative pressure to prevent

the H2O2 vapor from escaping through the building shell into the outdoor air.

The fumigation of the first of the seven zones was initiated in June 2003. Difficulties were

encountered in achieving the desired 216 ppm H2O2 in the zone. It became apparent that a major

reason for this problem was that the vapor-phase H2O2 was reacting more rapidly than

anticipated with the limited remaining building surfaces inside the empty zone, and perhaps with

the galvanized metal supply ducting. The supply ducting was replaced with (or lined with) highdensity polyethylene, considered to be less reactive with H2O2. Three of the 200,000 ft3

 zones

(including the first) were eventually further subdivided into two zones, with the new sub-zone
147

that was thus created ranging in size from 40,000 to 100,000 ft3

. The total number of treated

zones was thus increased from seven to ten. For some fumigations, the number of VHP

generators was increased, to increase capacity where necessary to maintain the concentration

above 216 ppm at one or more of the continuous monitors.

During all fumigation activities, sensitive H2O2 sensors were located at various positions outside

the building, along the fence-line, and on some neighboring buildings. At no time did any of the

fence-line monitors detect ambient H2O2 concentrations above background.

In August 2003, the last of the zones was successfully fumigated according to the specified

process conditions: $216 ppm H2O2 for 4 hours, $70 o

F, saturation level #80%. (Concentration,

temperature, and saturation typically varied within a zone during fumigation, but remained in the

specified ranges for 4 hours.) For all ten zones, chemical and biological indicator requirements

were also met. One zone had to be re-fumigated when one of the biological indicators showed

growth of the indicator organism, but all indicators tested negative after the second fumigation.

The difficulties that were encountered in maintaining the H2O2 concentration in some of the

zones during this fumigation underscore the need to more thoroughly understand the decay rate

of H2O2 upon contact with various building surfaces, and to ensure that adequate generation

capacity is available to compensate for the H2O2 losses that will result.

Significant post-fumigation environmental monitoring was conducted for B. anthracis, using

both surface sampling and aggressive air sampling techniques. The air sampling took place after

the interior surfaces of the zone to be sampled had been aggressively disturbed using a leaf

blower to re-suspend any residual spores. All 619 samples cultured negative for B. anthracis. 

On the basis that all environmental samples were negative for spore growth, and that the

fumigations had been successful in achieving both the target process conditions and the required

chemical and biological indicator results, the Environmental Clearance Committee concluded

that the remediation had been successful, and recommended in November 2003 that the facility

be re-opened. The Department of State subsequently renovated and refurbished the building,

incorporating a number of design and operational changes to better protect the workers should

such an incident ever reoccur in the future.

5.2.5 Concerns for the User

Hydrogen peroxide vapor is acutely toxic at high concentrations. The byproducts of the vapor

are harmless. The U.S. Occupational Safety and Health Administration (OSHA) has an eighthour Permissible Exposure Limit (PEL) for hydrogen peroxide gas of 1.0 ppm. The short-term

limit (Immediately Dangerous to Life or Health, or IDLH) is 75 ppm for a 30-minute exposure. 

One positive feature about this gas is that it is an irritant at levels above 1.0 ppm, minimizing the

inadvertent exposure to dangerous levels of the gas. The gas has a discernable, slightly pungent

or acidic odor at levels below the IDLH level, which adds to the safety factor.
148

5.2.6 Availability of the Technology for Commercial Applications

There are multiple vendors offering commercial H2O2 vapor systems for sterilizing relatively

small volumes, such as sterilization chambers and pass-through rooms. In addition, the

experience at the Department of State mail facility SA-32, and at GSA Building 410, has

demonstrated that it may be practical to adapt some of these commercial systems such that

volumes of 100,000 to 200,000 ft3

 can be treated, perhaps by the use of multiple generators. A

key consideration in this scale-up is the need to understand how rapidly the highly reactive H2O2

vapor will decay in contact with typical building surfaces, so that the generation capacity can be

reliably estimated for cases where the building is not as thoroughly gutted as SA-32 was.

5.2.7 Advantages and Disadvantages

There are three main advantages to this technology application. The first is that it has been

documented by many sources over a long period of time to be effective against viruses, bacteria,

and spores. The second is that the technology is currently available for implementation and

additional research. The third advantage is that the end products, after catalytic breakdown, are

water and oxygen.

One main disadvantages of this technology is that the vapor is reactive and can break down upon

contact with certain materials such as galvanized steel and porous surfaces such as paper and

unpainted cinderblock. The thought is that the high degree of surface area catalyzes the

conversion of the active gas to water and oxygen. This is thought to be the cause of the

difficulties encountered at SA-32, described in Section 5.2.4.2 above.

5.2.8 Potential Areas for Future Research

The issue of surface inactivation should be addressed by testing the reactivity of hydrogen

peroxide vapor with different common building materials and office products, determining the

sterilization capability on various surfaces found indoors. As with all scientific experimentation,

independent verification of the results is recommended. 

Scalability of the technology is another area for future research. It is not clear if the limitations

of size are a function of the generation of the vapor or the stability of the vapor. Clearly,

multiple H2O2 generation units could be linked together to generate vapor in a large enclosure, as

was done in SA-32, with a separate system to maintain negative air pressure of the larger

enclosure. The individual peroxide generators would be designed to remove the vapor in their

respective locations during the “aeration phase” following fumigation.

Another key area for future research is the compatibility of H2O2 vapor with the materials found

inside buildings, in particular, with sensitive equipment. This is an issue of concern for all

fumigants, not only hydrogen perioxide.
149

5.2.9 References for Section 5.2

Block, 2001. Block, S. S. “Peroxygen compounds.” In Disinfection, Sterilization and

Preservation, 5th ed. (S. S. Block, ed.), pp. 185-204. Lippincott Williams & Wilkins,

Philadelphia, PA, 2001.

Carlson and Raber, undated. Carlson, Tina; and Raber, Ellen “The Use of Vaporous Hydrogen

Peroxide for Building Decontamination.” Unpublished report, For Official Use Only. Lawrence

Livermore National Laboratory, Livermore, CA.

EPA, 2004a. Pesticides: Topical and Chemical Fact Sheets – Vaporized Hydrogen Peroxide. 

U.S. Environmental Protection Agency. Available at: 

www.epa.gov/pesticides/factsheets/chemicals/vhp_factsheet.htm. (Accessed December 2004).

EPA, 2004b. Pesticides: Topical and Chemical Fact Sheets – Hydrogen Peroxide and

Peroxyacetic Acid. U.S. Environmental Protection Agency. Available at:

www.epa.gov/pesticides/factsheets/chemicals/hydrogenperoxide_peroxyaceticacid_factsheet.ht

m (Accessed December 2004).

Kirk-Othmer, 1993. Encyclopedia of Chemical Technology, Fourth Edition, Volume 8,

“Disinfectants and Antiseptics.” Pages 255-256.

Kirk-Othmer, 1997. Encyclopedia of Chemical Technology, Fourth Edition, Volume 22,

“Sterilization Techniques.” Pages 832-851.

Klapes and Vesley, 1990. Klapes, N. A.; and Vesley, D. “Vapor-phase Hydrogen Peroxide as a

Surface Decontaminant and Sterilant,” Applied and Environmental Microbiology, 56(2): 503-

506 (1990).

Kokubo et al., 1998. Kokubo, M.; Inoue, T.; and Akers, J. “Resistance of Common

Environmental Spores of the Genus Bacillus to Hydrogen Peroxide Vapor.” Journal of

Pharmaceutical Science and Technology, 52(5): 228-231 (1998).

Lauderback et al., 2002. Lauderback, J.; Fraser, J.; Gustin, E.; McDonnell, G.; and Williams, K. 

“Point-of-Manufacture Sterilization,” Pharmaceutical and Medical Packaging News, October

2002. Available at: www.devicelink.com/pmpn/archive/02/10/005.html. (Accessed December

2004).

Loudoun County, Virginia, 2004. U.S. State Department Mail Facility Anthrax Cleanup: The

Latest News, www.co.loudoun.va.us/general/cleanup.htm. (Accessed December 2004).

Rickloff and Orelski, 1989. Rickloff, J.R.; and Orelski, P.A. “Resistance of Various

Microorganisms to Vaporized Hydrogen Peroxide in Prototype Tabletop Sterilizer,” presented at

the 89th Annual Meeting of the American Society of Microbiologists, New Orleans, May 1989.

SAIC, 2003. Personal communication with Dr. Peter Burke, STERIS Corporation.
150

Schrodt, 1883. Schrodt, M. “Ein neues Konservierungsittel fur Milch und Butter,” Milch-Zig,

13: 785 (1883).

Sias, 2003. Sias, Ralph. “Biological Organism Reduction with Hydrogen Peroxide,” Advancing

Applications in Contamination Control, January 2003. Available at:

www.a2c2.com/articles/lifejan02.asp?pid=328&articleText=lifejan02. (Accessed December

2004).

STERIS, 1996. Cycle Development Guide for VHPTM 1000 Biodecontamination System, pp.

129372-711. STERIS Corporation, Mentor, OH. February 23, 1996.

STERIS, 2004. “Vaporized Hydrogen Peroxide Decontamination Systems.” STERIS Corp.,

Mentor, OH. Available at: www.steris.com/defense_industrial/pro_vhp.cfm. (Accessed

December 2004).

Von Bockleman and von Bockleman, 1972. von Bockelman, I.; and von Bockleman, B. “The

Sporicidal Action of Hydrogen Peroxide, A Literature Review,” Lebensmittel-Wissenschott

Technologies, 5: 22 (1972).

West Dugway Test Center, 2002. “Abbreviated Test Report for the Validation of Chlorine

Dioxide Decontamination,” Test Project No. 8-CO-210-000-084, WDTC Document No. WDTCTR-02-059. (Note: Contents of the cited report appearing in the current document are used by

permission. Requests for the entire document should be referred to the U.S. EPA, Region 8,

8EPR-ER, 999 18th Street, Suite 300, Denver, CO 80202.)
151

5.3 Paraformaldehyde

Paraformaldehyde is a polymerized form of formaldehyde, (CH2O)n. It is a stable white

crystalline powder. Upon heating, it generates formaldehyde gas, which has antimicrobial

properties. The antimicrobial properties of formaldehyde are believed to result from its

reactivity in the alkylation of proteins, nucleic acids, and DNA and RNA (Wickramanayake,

1990). Because pure formaldehyde is unstable at ambient temperatures (resulting in

polymerization), and is not commercially available (Kirk-Othmer, 1994), paraformaldehyde is a

material which can provide a readily-usable form of formaldehyde at use sites. Both

paraformaldehyde and formaldehyde have been used in decontamination for more than 30 years,

although the extent of this use (e.g., annual use quantities) is largely unknown.

5.3.1 Description of the Technology Alternative

Paraformaldehyde is used to generate formaldehyde gas for the decontamination of rooms,

storage cabinets, and equipment. A typical procedure for the use of paraformaldeyde is to isolate

the material or area being sterilized (e.g., sealing with tape or sheeting), using hot plates to

sublimate the paraformaldehyde and fans to distribute the vapor within the space for a specified

time period, and finally to introduce a compound that will neutralize the formaldehyde vapor

once treatment is complete (Munro et al., 1999). The standard method for neutralizing the

formaldehyde is the use of ammonia generated by the heating of ammonium bicarbonate.

Alternatively, a more sophisticated approach – particularly applicable when treating larger

volumes – is to use a formaldehyde generator. In a generator, the heating of the

paraformaldehyde takes place inside a closed system, and the resulting formaldehyde is

introduced into the room to be treated (Certek, 1980). One vendor of such generators is Certek

Inc.

Following removal of formaldehyde gas, some studies report that surfaces are cleaned with

water to remove any remaining residue. In particular, high humidity or high concentrations can

result in either the precipitation of paraformaldehyde or the condensation of formaldehyde in

water. Condensed formaldehyde/water mixtures would likely result in paraformaldehyde

deposits on the surfaces after the water evaporated (Hoffman and Spiner, 1990).

In addition to paraformaldehyde, formalin has also historically been used as a source of airborne

formaldehyde for sanitizing or decontamination purposes. Formalin is a 37 percent aqueous

solution of formaldehyde, stabilized by small quantities of methanol. Formalin is dispersed into

the air such as through a fogging apparatus (Wickramanayake, 1990). Because both

paraformaldehyde and formalin generate formaldehyde as the active ingredient, this chapter

addresses both the use of formalin fog and the use of paraformaldehyde to generate

formaldehyde gas for building decontamination, but with emphasis on the latter methodology.
152

5.3.2 Technical Maturity

Paraformaldehyde vaporization is fully mature and has been routinely used worldwide for

sanitizing and disinfecting rooms and equipment in the health services industry (Coldiron and

Janssen, 1984) and in U.S. Army Medical Research Institute of Infectious Diseases

(USAMRIID) biological laboratories (Alexander, 1998). It was also used to decontaminate two

pieces of postal equipment, which had been enclosed within a fumigation tent, in the Department

of Justice mail facility in Landover, MD, which had become contaminated with B. anthracis

spores in connection with the October 2001 anthrax mail incident.

Paraformaldehyde technology has been applied to rooms and small spaces (such as laboratories

and safety cabinets), and to individual equipment items enclosed in chambers or tents. However,

it has been used in at least one building decontamination project. The fumigant was used to

destroy Ebola virus throughout the Hazelton Research Center in Reston, Virginia. A

concentration of 12,000 mg/m3

 paraformaldehyde was used for the building. The size of this

building was not given, but – based on the back-calculation from other available data – it was

estimated to be 78,000 ft3

 (2,200 m3) (Alexander, 1998).

5.3.3 Applications of the Technology

Paraformaldehyde (a solid) is used as a source of either gaseous formaldehyde or solution

(aqueous) formaldehyde. When the crystalline paraformaldehyde powder is heated, it releases

formaldehyde gas. When dissolved in water, paraformaldehyde behaves like aqueous methanolfree formaldehyde.

Both paraformaldehyde and formaldehyde are primarily used in resin manufacturing, for uses

such as adhesives and binders in consumer and industrial applications. Paraformaldehyde is

used by resin manufacturers seeking low water content or enhanced reaction rate control, and in

the production of phenol-, urea-, resorcinol-, and melamine-formaldehyde resins (Kirk-Othmer,

1994). Paraformaldehyde is also used in dentistry as a fixative. In these applications, the

paraformaldehyde is dissolved in a solution to prepare aqueous formaldehyde.

Paraformaldehyde was registered by EPA under FIFRA as a sanitizer and fungicide for use on

barber and beauty shop equipment in 1964. Since then, it has been registered and used as a

disinfectant, sanitizer, fungicide, and microbicide in household and domestic dwellings, in ships

and ship holds, on bedding and clothing, and in non-food/non-feed-transporting trucks (EPA,

2004). It is unclear which of these applications use aqueous formaldehyde and which use

gaseous formaldehyde.

Under FIFRA definitions, a “sanitizer” is defined as a substance that significantly reduces

bacterial populations, but does not destroy all bacteria or other microorganisms. A

“disinfectant” destroys a specific species of microorganism – in particular, infectious (viral)

microorganisms – but not necessarily bacterial spores. A “sterilant” destroys all forms of

microorganisms, including all vegetative bacteria, bacterial spores, fungi, fungal spores, and

viruses. Paraformaldehyde has never been registered as a sterilant, although it has been

demonstrated to be effective in killing B. anthracis spores under certain prescribed conditions.
153

Paraformaldehyde has been used as a fumigant for more than 30 years. It has been used to

decontaminate laboratory facilities and to disinfect sickrooms, clothing, linen, and sickroom

utensils (EPA, 2004). In these applications, paraformaldehyde is heated to form gaseous

formaldehyde.

Paraformaldehyde was registered and used to control microbial growth in laboratories and to

decontaminate animal facilities until recently, when all registrations for this use of the chemical

were canceled due to nonpayment of fees by the manufacturer (the name of the manufacturer

was not identified in the source). Quarantine use of paraformaldehyde has been allowed in a

poultry health laboratory in Arkansas (a use which was in effect through June 15, 2004). 

Similarly, the Department of Defense was authorized to utilize paraformaldehyde for quarantine

use since 1993 (effective until July 6, 2002). Similar exemptions for the use of

paraformaldehyde to decontaminate high-containment microbiological laboratories at Plum

Island, NY, and Ames, IA (effective until June 15, 2001) have also been granted to the USDA

(EPA, 2004).

A related use of gaseous formaldehyde is in low temperature steam formaldehyde (LTSF)

technology, a technique for decontamination of small items developed in the late 1960s. In this

method, small non-disposable items are placed inside an apparatus which uses sub-atmospheric

(i.e., relatively low temperature) steam and gaseous formaldehyde. Typical conditions include

temperatures of 73 °C and formaldehyde levels of 8,000 mg/m3

 (Hoxey et al., 1985). These

temperatures are impractical for larger scale (e.g., room) decontamination.

5.3.4 Evaluation of Available Data

More than 30 years of performance data regarding paraformaldehyde decontamination are

available, most in small-scale applications in clinical or research settings. This is likely to be a

reflection of its long use in the medical services industry for decontamination of biological

safety cabinets, laboratories, and reusable equipment.

While much of the testing and application of paraformaldehyde has focused on microorganisms

other than (or in addition to) bacterial spores, some of this testing has utilized bacterial spore

strips as a convenient means for assessing the antimicrobial impacts of fumigant. Among the

spores utilized in this spore strip testing are B. stearothermophilus, B. subtilis, and B. globigii (B.

subtilis v. niger).

In one study addressing spores directly, aqueous formaldehyde was used in the treatment of soil

contaminated with B. anthracis (Manchee et al., 1994). No data were reported from this study

relevant to the use of gaseous formaldehyde against this organism.

Coldiron and Janssen (1984) describe an example of paraformaldehyde use in decontaminating a

hospital autopsy suite at the University of Texas. This area consisted of three rooms, 73 meters

of connecting exhaust ductwork, and three exhaust air incinerators. Concerns were for various,

unidentified microorganisms present throughout the suite, as a result of prior use, which would

pose potential risks to construction personnel. Commercially available indicator strips of B.

stearothermophilus and B. globigii were used to determine disinfection completeness. Based on
154

Figure 5.3-1. Percent Survival of Test Organisms after Decontamination with

Various Concentrations of Formaldehyde. 

Survival was measured as a percentage of the growth (CFU or TCID50) of that for the untreated control for

each test organism. The data were for test pieces placed inside the cabinet on the side wall. (The relative

humidity was <58 percent, and the temperature was <27 °C.) (Munro et al., 1999)

‘no growth’ results of the test strips placed throughout the room, successful decontamination

resulted from the use of 10.6 to 17.7 g/m3 paraformaldehyde, 3 to 4 hours of contact time, and

relative humidity of 65 percent (Coldiron and Janssen, 1984). 

Munro et al. (1999) conducted tests to determine optimum decontamination conditions for metal

biological safety cabinets using paraformaldehyde. Organisms tested included polio virus,

Mycobacterium bovis bacillus Calmette-Guérin (BCG), B. stearothermophilus, and B. subtilis. 

All testing was conducted on stainless-steel coupons placed at various locations inside a metal

cabinet. Optimal decontamination conditions were identified as 66 percent relative humidity, a

minimum temperature of 28 °C, and a paraformaldehyde concentration of 10.5 grams/cubic

meter. Figures 5.3-1 to 5.3-3 display the results of these studies, with independent variables of

concentration, relative humidity, and temperature, respectively (a 15 hour decontamination time

was used for all studies). The dependent variable in each case (percent survival) was measured

as the ratio of growth on the treated coupons versus growth on untreated controls (Munro et al.,

1999). Growth was measured in terms of 50 percent tissue culture infected dose (TCID50) for

polio, and colony-forming units (CFU) for other organisms. Figures 5.3-1 and 5.3-2 show that

the effectiveness of decontamination increased with concentration and humidity, while effects of

temperature resulted in marginal variability based on Figure 5.3-3. Table 5.3-1 shows the

survival of organisms as a function of location in the cabinet. The authors conclude that B.

stearothermophilus was killed more readily than B. subtilis, although completely successful

decontamination (total kill) was demonstrated for 7 of 144 coupons containing B. subtilis.
155

Figure 5.3-2. Percent Survival of Test Organisms after Decontamination at Various

Relative Humidities. 

Paraformaldehyde weights were $5 g/m3, and the temperature was approximately 25 °C. (Munro et al.,

1999)

Figure 5.3-3. Percent Survival of Test Organisms with Variation of Temperature

During Decontamination with Paraformaldehyde at 10.5 G/m3

 and a Relative

Humidity of Approximately 58 Percent. (Munro et al., 1999)
156

Table 5.3-1. Survival of Test Organisms on Strips Positioned at Different Test Locations

During Decontamination a

Location of strip B. subtilis

(CFU)

B. stearothermophilus (CFU) BCG

(CFU)

Polio virus (TCID50/0.2

ml) 

Under the cabinet

tray

15,000 47.4 <10 0 

Cabinet tray 20,000 46 <10 0 

Cabinet side 21,000 73.8 <10 0 

Beyond the exhaust

filters

19,000 293.2 <10 100.66

Initial inoculation

level

1.76x106 4x105 1.39x106 1012.5

a. Data are averages of three determinations. Decontamination conditions were as follows: paraformaldehyde, 10.6 g/m3

; relative humidity, 57%; temperature, 28 °C; time, 15 hours. (Munro et al., 1999).

Table 5.3-2 provides additional data summarized by G.B. Wickramanayake (1990). The

formaldehyde concentrations and decontamination time for testing are much lower than used by

Munro et al. above, but nevertheless show inactivation to some degree. In particular, Table 5.3-

2 shows 6-log inactivation of B. subtilis which is apparently higher than the results by Munro et

al. (1999), despite the higher concentrations and increased decontamination times used by

Munro.

Table 5.3-3 presents data by V.H. Lach (1990), which provides results of five different

procedures in decontaminating a 38 m3

 test room, using either formalin or paraformaldehyde as a

source of formaldehyde. Part of the purpose of this work was to attempt to reproduce conditions

of previous studies, such as Taylor (1969), discussed below. Therefore, comparisons of results

between these studies are useful in assessing reproducibility. Unfortunately, the author noted

that the low kill rate observed for the paraformaldehyde test in Table 5.3-3 was due to

difficulties in simulating the conditions and formaldehyde release rate between the two tests.

Based on the results by Lach, the author notes that the theoretical airborne concentration of

formaldehyde (i.e., based strictly on quantity introduced divided by room volume) was always

significantly greater than the measured concentrations. A possible explanation for this includes

the condensation of water and formaldehyde, in which case the use of lower quantities of

formaldehyde could result in the elimination of condensed quantities. If this were true, a lower

formaldehyde feed rate could have an effectiveness equivalent to a higher feed rate, if the losses

due to condensation are eliminated at the lower rate. Such a hypothesis would require testing. 

Many variations in decontamination as a function of bacteria or toxin placement were tested at 

Fort Detrick, Maryland (Taylor et al., 1969). The results of these tests are shown in Table 5.3-4. 

As shown, materials tested included laboratory equipment and various surfaces, while the size of

the facilities also varied from small to large rooms. For experiments involving rooms, test strips

containing the organism were typically placed at various locations inside the room.
157

Table 5.3-2. The Effects of Formaldehyde on Various Organisms

Organism Matrix Formaldehyde

Concentration

Temp.

(/C)

Relative

Humidity

(%)

Time InactivationSource

Bacteria

E. coli Dried on

steel rings

20 mg/m3 20 to 27 80 10 min 90% (1)

E. coli Dried on

steel rings

180 mg/m3 20 to 27 80 <3

min

90% (1)

B. globigii Dried on

steel rings

20 mg/m3 20 to 27 80 120

min

90% (1)

B. subtilis Not

identified

300 mg/m3 20 100 1.5 hr 99.9999% (2)

Fungi

A. sydowi Dried

spores

2.5 mg/m3 20 to 22 65 24 hr 99.99% (3)

A. flavus Dried

spores

2.5 mg/m3 20 to 22 65 24 hr 99.99% (3)

A. candidus Dried

spores

2.5 mg/m3 20 to 22 65 24 hr 99.99% (3)

Scopuloriopsis

brevicaulis

Dried

spores

2.5 mg/m3 20 to 22 65 24 hr 99.99% (3)

Paecilomyces

varioti

Dried

spores

2.5 mg/m3 20 to 22 65 24 hr 99.99% (3)

A. sydowi In dust

samples

2.5 mg/m3 20 to 22 65 24 hr 17% (3)

A. repens In dust

samples

2.5 mg/m3 20 to 22 65 24 hr 96% (3)

A. chevalieri In dust

samples

2.5 mg/m3 20 to 22 65 24 hr 82% (3)

A. versicolor In dust

samples

2.5 mg/m3 20 to 22 65 24 hr 50% (3)

Source: Tables 4 and 6 of Wickramanayake (1990). The Wickramanayake article summarizes data

previously published in the following sources, which were not reviewed for the present report): (1)

Bovallius and Anas,1977; (2) Caputo and Odlaug, 1983; and (3) Klein and Deforrest, 1983.
158

Table 5.3-3. Measured Average Conditions and Experimental Kill of B. Globigii

Formaldehyde

Source

Time

(hr)

Matrix Formaldehyde

Concentration (mg/m3)

Relative

Humidity

(%)

Kill (log10 cycles)

Theoretical Measured

Formalin 18 Filter discs 7,060 240-800 89 to >99 >9 (all five locations)

Formalin 2.5 Filter discs 7,060 339-1,100 45 to 74 5 to >9

Paraformaldehyde 2.5 Filter discs 10,600 393-805 35 to 42 4 to 5 a

Formalin 3 Filter discs 2,830 102-261 91 to >99 6 to >9

Formalin 18 Filter discs 2,830 89-347 84 to >99 >9 (all five locations)

Source: Lach, 1990. In each test, five sensors were placed throughout a 38m3 test room. The above results

display the ranges of the average measurements. Organism levels varied from 102 to 3 x 108

. For all room

locations in each experiment, temperature varied over a narrow range of 23.2 to 25.8 °C.

 a. Low kill rates due to difficulties in replicating target conditions.

For experiments involving pieces of equipment or smaller surfaces, the organism was typically

dispersed in air and allowed to settle, with subsequent testing performed by swabs or similar

means. The last column of Table 5.3-4 assists in identifying the procedures used. In all cases,

the authors note that “the microorganisms were killed and the toxin was detoxified.” However,

while initial levels of the microorganisms were presented (most tests ranged from 104

 to 107

spores per mL), numerical results regarding the remaining spores were not available and

therefore log-kill data cannot be determined.

Tables 5.3-5 to 5.3-7 show experimental test data of the survival of B. subtilis versus variables of

time and relative humidity for three different types of stopper closures. These closures are

intended to investigate the ease with which formaldehyde can penetrate different materials. The

spores were present inside the test tubes. The study, conducted by Hoffman and Spiner (1970) at

Fort Detrick, Maryland, provides insight into the penetrating ability of formaldehyde through

these materials, rather than the ability of formaldehyde to treat organisms embedded onto these

materials. Some conclusions from the authors and from the presented data include the

following:

• Higher levels of formaldehyde (10.6 g/m3

 versus 3.5 g/m3) result in faster bacteria

kill, and higher exposure times result in higher levels of kill. These results are

somewhat obvious and expected.

• At a formaldehyde concentration of 3.5 g/m3, intermediate relative humidities

(i.e., 33 to 75 percent) are best for penetrating paper, while very high humidity

(i.e., 100 percent) is best for glassine penetration and very low humidity (11

percent) is best for cotton penetration. Similar conclusions were found for

formaldehyde levels of 10.6 g/m3

, with the exception that there was no significant

difference in paper penetration for relative humidity between 33 and 100 percent.
159

Table 5.3-4. Paraformaldehyde Sterilization of Facilities, Materials, and Equipment

Organism Description

of Facility

Tested

Facility

Volume

(m3)

Paraformaldehyde

Conc.

(g/m3)

Temp.

(/C)

Relative

Humidity

(%)

Contact

Time

(hours)

# Organism

Locations in

Test; Viable

Recoveries/

Total Tests

Conducted

B. subtilis Laboratory

room

64 10.7 23.3 60 1 15; 0/5

Serratia

marcescens

15; 0/5

B. subtilis Laboratory

room

130 10.7 23.3 60 1 15; 0/5

S.

marcescens

15; 0/5

B. subtilis Mobile

laboratory

trailer

62 5.4 23.3 60 1 20; 0/5

B. subtilis Two large

connected

rooms, of 4 to

5 stories each

1,904 8.6 31 50 to 55 2 200; 0/1

B. subtilis 15 types of

surfaces a

in 0.71 m3

chamber

10.7 24 60 1 to 2 (dispersed on

each

surface); 0/5

B. subtilis Within filter

media of a

class I storage

cabinet

in 1.3 m3

cabinet

10.7 24 60 1 24; 0/5

B. subtilis Vaccine tubes in 0.06 m3

chamber

10.7 Not

given

60 1 (dispersed on

surfaces); 0/2

S.

marcescens

Vaccine tubes in 0.06 m3

chamber

10.7 Not

given

60 1 (dispersed on

surfaces); 0/2

B. subtilis Miscellaneous

electronic

laboratory

equipment

2.8 to 14 10.7 ~24 >50 1 to 2 (dispersed on

surfaces);

0/10

Newcastle

disease

virus

Interior

surface of test

chamber

0.03 10.7 24 60 1 (dispersed on

surface) 0/1

Newcastle

disease

virus

Class I storage

cabinet

1.2 10.7 24 60 0.5 6; 0/1

C.

botulinum

toxin type A

Air sampler

equipment

in 0.08 m3

chamber

10.7 24 70 to 80 2 (dispersed on

surfaces); 0/3
Organism Description

of Facility

Tested

Facility

Volume

(m3)

Paraformaldehyde

Conc.

(g/m3)

Temp.

(/C)

Relative

Humidity

(%)

Contact

Time

(hours)

# Organism

Locations in

Test; Viable

Recoveries/

Total Tests

Conducted

160

C.

botulinum

toxin type A

Powder

samples (10

mg)

in 0.03 m3

chamber

10.7 23 60 4 1; 0/3

C.

botulinum

toxin type A

Powder

samples (20

mg)

in 0.03 m3

chamber

7.1 24 45 48 1; 0/1

Source: Taylor et al., (1969).

 a. The surface types tested were glass, rubber, plastic, stainless steel, galvanized metal, wood, paper, sponge,

filter paper, painted surface, rigid plastic, copper, aluminum, vinyl sheeting, and mild steel.

Table 5.3-5. Percent Recovery of B. subtilis in Test Tubes with Paper Closures

Exposure Time (hr) RH=11% RH=33% RH=53% RH=75% RH=100%

1 47.1 35.4 50.3 12.8 52.3

2 10.9 2.6 3.9 2.2 4.2

3 3.9 0.34 0.092 0.005 0.69

4 0.37 0.24 0.008 0.0003 0.15

7 0.0035 0.00015 0.0005 0 0

17 0.0008 0 0 0 0

Source: Hoffman and Spiner, 1970.

 Spores were present in test tubes with indicated closure; test tubes were enclosed in a small testing

chamber with 3.5 g/m3

 formaldehyde gas generated from paraformaldehyde at 25 °C.
161

Table 5.3-6. Percent Recovery of B. subtilis in Test Tubes with Glassine Closures

Exposure Time (hr) RH=11% RH=33% RH=53% RH=75% RH=100%

1 80.8 74.2 100 99.0 72.8

2 46.3 64.2 77.5 64.7 27.7

3 27.1 61.3 85.2 34.6 6.6

4 3.2 24.1 35.5 40.3 2.0

7 0.018 4.9 30.3 2.9 0.0005

17 0.0016 0.005 2.3 0 0

Source: Hoffman and Spiner,1970. Spores were present in test tubes with indicated closure; test tubes were

enclosed in a small testing chamber with 3.5 g/m3

 formaldehyde gas generated from paraformaldehyde at

25 °C.

Table 5.3-7. Percent Recovery of B. subtilis in Test Tubes with Cotton Plug Closures

Exposure Time (hr) RH=11% RH=33% RH=53% RH=75% RH=100%

1 62.9 71.6 96.5 82.9 99.1

2 20.4 41.2 57.3 76.3 97.5

3 7.0 27.6 43.6 48.9 100

4 0.6 11.0 57.6 47.7 85.0

7 0.0056 0.061 9.1 9.8 30.8

17 0.0003 0 0 0 0.022

Source: Hoffman and Spiner, 1970. Spores were present in test tubes with indicated closure; test tubes were

enclosed in a small testing chamber with 3.5 g/m3

 formaldehyde gas generated from paraformaldehyde at

25 °C.

The differences in results by Hoffman and Spiner (1970) regarding penetration ability are likely

to cause difficulty in applications of building decontamination. Of the large variety of materials

potentially present in such a situation, these results indicate that there is no single ‘ideal’

condition in treating them. The different materials present alternately may be best treated at

either low, moderate, or high relative humidity. On the other hand, for general ambient room

decontamination results from authors such as Coldiron and Janssen (1984) and Munro et al.

(1999), there is agreement that an intermediate relative humidity (e.g., 60 to 70 percent) is

effective. In attempting to apply these various results to building decontamination, consideration

could be made to the application of a variety of humidity conditions. For example, humidity

could be maintained at one level for a period of time followed by a period of time with different

humidity.

Reflecting the experience with fumigations utilizing paraformaldehyde, several organizations

have issued procedures, guidelines, and regulations pertaining to its use for the treatment of
162

various enclosed spaces (NIH, 1979), containment areas (USAMRIID, 1999), and biosafety

cabinetry (NSF, 2002).

Experience at the Department of Justice mail facility

The mail processing facility within the Department of Justice’s Landover Operations Center

(LOC) in Landover, MD, became contaminated with B. anthracis spores during the October

2001 anthrax mail incident, probably through the processing of cross-contaminated mail. The

contamination was discovered through precautionary environmental surface sampling that was

undertaken after the contamination at the USPS Brentwood P&DC was detected. This sampling

indicated that the B. anthracis contamination was limited to the mail facility portion of the LOC,

and had not spread to other portions of the LOC warehouse.

Accordingly, the mail facility was isolated from the remainder of the warehouse using barriers

consisting of plywood and polyethylene sheeting. The mail facility was exhaust ventilated using

three exhaust fans exhausting through a HEPA filter, to keep the mail facility under negative

pressure relative to the remainder of the LOC, and to thus prevent the spores from spreading to

other parts of the building.

For source reduction, essential items (e.g., certified mail receipts) were packaged and shipped

off-site for ethylene oxide fumigation and re-use. Non-essential porous items were cleaned to

the extent possible – usually with 0.5% bleach solution or HEPA vacuuming – packaged, and

shipped off-site for disposal. Items that were thus removed and sent for disposal included

carpeting, upholstered furniture, non-essential paper, personal effects, and workstation cubicles.

Most non-porous surfaces were sprayed with aqueous chlorine dioxide solution or a surfactant

solution, and wiped down following a 30-minute contact period. These surfaces included the

floor, walls, counters, shelves, and non-porous furniture (desks and file cabinets). Non-porous

ceilings and HVAC ductwork were not cleaned.

Paraformaldehyde fumigation was used to treat two pieces of postal equipment, the mail sorter

and the stamping machine. Fumigation was selected for this equipment because they contained

intricate components and difficult-to-reach areas that would have been impossible to

decontaminate using a liquid, except by disassembling the machine. The two pieces of

equipment were enclosed within a single tent (approximate volume 8,300 ft3

) inside the mail

room, constructed using 2- by 4-inch wood framing and a double layer of 6-mil polyethylene

sheeting. EPA issued a crisis exemption under FIFRA to allow paraformaldehyde to be used in

this application.

Multiple pans containing Hoechst-Celanese paraformaldehyde (95% pure) were placed on hot

plates inside the tent. An excess of paraformaldehyde – beyond the minimum 0.3 g of

paraformaldehyde per cubic foot of tent volume (NIH, 1979; USAMRIID, 1999; NSF, 2002) –

was placed on the hot plates such that the formaldehyde concentration inside the tent would be

maintained at the required level (about 8,900 ppm) for the required 12-hour exposure period. An

airless sprayer released a water mist into the tent as required to maintain the RH above 50%.
163

When each stage of the fumigation was over, hot plates inside the tent were activated that

contained ammonium bicarbonate (1.5 g of ammonium bicarbonate per gram of paraformaldehyde). After the vaporized NH4HCO3 neutralized the formaldehyde inside the tent, the tent

was vented to the outdoor air.

The 12-hour fumigation process consisted of two 6-hour treatments. After the first 6-hour

fumigation stage was completed, the formaldehyde neutralized, and the tent ventilated, the postal

equipment was operated in order to aerosolize any spores remaining within the two machines so

that these residual spores would be susceptible to destruction in the second fumigation stage.

Following the remedial activities, the success of the remediation was determined through

environmental sampling, mostly surface wipe sampling but also including some vacuum sock

sampling. All samples were negative for growth of B. anthracis.

After the environmental sampling had proven negative for B. anthracis, the fumigated sorting

machine was disassembled and further wiped clean prior to re-use.

5.3.5 Concerns for the User

From a practical standpoint, concerns for paraformaldehyde are similar to those for

formaldehyde. This is because paraformaldehyde will generate gaseous formaldehyde during

storage or use. If it gets in contact with water, paraformaldehyde will similarly break down to

formaldehyde. In addition, toxicological data or health concerns regarding paraformaldehyde

are not readily available. For these reasons, information in this section will be generally limited

to formaldehyde.

Formaldehyde has been identified as a probable human carcinogen by EPA, based on limited

evidence of carcinogenicity in humans through inhalation exposure, and sufficient evidence for

carcinogenicity in experimental animals. It produces nasal carcinomas in rats (EPA, 2003). 

Acute effects include respiratory irritation.

Airborne occupational exposure limits for formaldehyde applicable to the United States are as

follows (NIOSH, 2003):

• NIOSH REL 8-hour TWA 0.016 ppm (0.02 mg/m3

)

• OSHA PEL 8-hour TWA 0.75 ppm (0.92 mg/m3) 

• ACGIH TLV 15-minute short term exposure limit (STEL) ceiling 0.3 ppm (0.4

mg/m3

)

• Immediately Dangerous to Life or Health (IDLH) Level 20 ppm (25 mg/m3

).

These exposure limits are several orders of magnitude below the concentrations used for

decontamination as discussed above. Therefore, following decontamination, steps must be taken

to completely neutralize excess formaldehyde in the air as well as to similarly remove any

chemical which may have condensed onto surfaces. Formaldehyde is a flammable, colorless gas

(lower explosive limit of 7 percent) with a pungent odor, all of which reflect additional concerns

during use. Crystal paraformaldehyde itself is also combustible, with a flash point of 70 °C. 
164

While the lower explosive limit and the flash point are well above the typical concentration and

temperature conditions encountered during use, precautions must be taken for the possibility of

extreme localized conditions in a room (e.g., in the immediate vicinity of the gas generation

source or in a poorly ventilated area within a room). Formaldehyde gas has a density only

slightly higher than that of air (relative vapor density 1.04); because of this similarity no

significant difficulties in mixing or partitioning would be expected.

Caution must be taken while handling paraformaldehyde as it decomposes to formaldehyde gas

on contact with water or moist air. Personal protection and exposure controls to be employed

while handling paraformaldehyde include the use of chemical goggles, full-face shield or a fullface respirator, impervious gloves and boots of chemically resistant material, and body suits,

aprons, or coveralls of chemical resistant material. Ventilation requirements for the use of

paraformaldehyde include mechanical ventilation, process or personnel enclosure, and control of

process conditions. There should also be a sufficient supply of replacement air to make up for

air removed by exhaust systems (ClearTech, 2003).

5.3.6 Availability of the Technology for Commercial Applications

This technology is readily available for commercial applications. The heating and dispersion of

paraformaldehyde is relatively straightforward. Technology for preparation (e.g., sealing

buildings) is routine and similar to what is required for other fumigants. Personal protective

equipment requirements are similar to other toxic materials. Monitors for formaldehyde gas

(providing real-time data) are commercially available.

As indicated previously, paraformaldehyde can be dispersed using a specially-designed

generator or a series of low-cost hotplates. Generator cost varies based on size requirements. 

The largest available generator by one manufacturer, Certek, is designed to decontaminate a

10,000 ft3

 (280 m3) area with a concentration of 10.6 g/m3 (identified as the NIH recommended

level). Room volume and concentration are related, so that if a lower concentration is targeted, a

larger room could be decontaminated. The cost for this type of generator is approximately

$60,000 and the cost of paraformaldehyde is approximately $24/ pound for small quantities

(bulk chemical quantities are cheaper) (SAIC, 2003). As an example, approximately six pounds

of paraformaldehyde would be required in decontaminating a room volume of 280 m3

 at a

concentration of 10.6 g/m3. In decontaminating a larger area such as a building, either multiple

generators could be used or the area can be decontaminated in sections.

5.3.7 Advantages and Disadvantages

Paraformaldehyde and formaldehyde have been used for equipment and room decontamination

for many years and therefore benefit from having a ‘track record.’ Advantages of formaldehyde

gas (such as that generated from paraformaldehyde) include that it is a powerful disinfectant,

noncorrosive to metals, and relatively easy to generate from either paraformaldehyde or formalin

(Coldiron and Janssen, 1984). 

A principal disadvantage is that – unlike the other fumigants covered in this report –

formaldehyde is a probable human carcinogen. The other fumigants are toxic at fumigation
165

concentrations, but they have not been adequately studied to determine carcinogenicity, and thus

are of lower-level concern.

5.3.8 Potential Areas for Future Research

Although vapor formaldehyde sterilization has been studied for many years, there is some

disparity regarding the concentrations needed to achieve effective decontamination. For

example, studies by Munro et al. (1999) identified an optimum concentration as 10,500 mg/m3

for organisms such as B. subtilis, while other studies such as Lach (1990) identified that

concentrations in the range of 100 to 1,000 mg/m3

 were effective for B. globigii. The

combination of gas concentration, relative humidity, temperature, and contact time that is

optimally effective for inactivating B. anthracis and surrogates needs to be determined.

In addition, most data available are for organisms on spore strips or on nonporous substrates

such as metal. The effectiveness of paraformaldeyde appears to vary, depending on the

composition and porosity of the surface being treated. There is a need to better quantify the

efficacy of this fumigant on a variety of hard, non-porous (e.g., metal, painted surfaces, glass)

and porous (e.g., wood, carpeting) surfaces.

Further studies are needed of the effects of formaldehyde on the functioning and lifetime of

sensitive electronic equipment.

5.3.9 References for Section 5.3

Alexander, 1998. Alexander, Lexi. “Decontaminating Civilian Facilities: Biological Agents and

Toxins.” Institute for Defense Analysis, unpublished report.

Bovallius and Anas, 1977. Bovallius, A.; and Anas, P. “Surface-Decontaminating Action of

Gluteraldehyde in the Gas-Aerosol Phase,” Appl. Environ. Microbiol., 34(2): 129 (1977).

Caputo and Odlaug, 1983. Caputo, R. A.; and Odlaug, T. E. “Sterilization with Ethylene Oxide

and Other Gases.” In Disinfection, Sterilization, and Preservation, 3rd edition (S. S. Block, ed.),

p. 47. Lea & Febiger, Philadelphia, PA, 1983.

Certek, 1980. “Apparatus for biological decontamination and subsequent neutralization of a

space,” U.S. Patent No. 4241020, James Grantham (Certek, Inc.). December 23, 1980.

ClearTech, 2003. Material Safety Data Sheet: Paraformaldehyde, ClearTech Industries Inc.

www.ClearTech.ca/inside/msds/pfmd-04-07-2003.pdf. Accessed December 2004.

Coldiron and Janssen, 1984. Coldiron, V.R.; and Janssen, H. Erle. “Safe Decontamination of

Hospital Autopsy Rooms and Ventilation System by Formaldehyde Generation.” Am. Ind. Hyg.

Assoc. J., 45(2); 136-137 (1984).

EPA, 2004. Formaldehyde. Integrated Risk Information System (IRIS), U.S. Environmental

Protection Agency. Available at: www.epa.gov/iris/subst/0419.htm. Accessed December 2004.
166

EPA, 2004. U.S. Environmental Protection Agency: Pesticides - Topical and Chemical Fact

Sheets: Paraformaldehyde. Available at:

www.epa.gov/pesticides/factsheets/chemicals/paraformaldehyde_factsheet.htm. Accessed

December 2004.

Hoffman and Spiner, 1970. Hoffman, Robert K.; and Spiner, David R. “Effect of Relative

Humidity on the Penetrability and Sporacidal Activity of Formaldehyde.” Applied Microbiology

20 (4): 616-619 (1970).

Hoxey et al., 1985. Hoxey, E.V.; Soper, C.J.; and Davies, D.J.G. “Biological Indicators for Low

Temperature Steam Formaldehyde Sterilization: Effect of Defined Media on Sporulation,

Germination Index and Moist Heat Resistance at 110 °C of Bacillus Strains.” Journal of Applied

Bacteriology, 58: 207-214 (1985).

Kirk-Othmer, 1994. Encyclopedia of Chemical Technology, Fourth Edition, Volume 11,

“Formaldehyde.” Page 931.

Klein and Deforrest, 1983. Klein, M.; and Deforrest, A. “Principles of Viral Inactivation.” In

Disinfection, Sterilization, and Preservation, 3rd edition (S. S. Block, ed.), p. 422. Lea &

Febiger, Philadelphia, PA, 1983.

Lach, 1990. Lach, V.H. “A Study of Conventional Formaldehyde Fumigation Methods.” 

Journal of Applied Bacteriology, 68: 471-477 (1990).

Manchee et al., 1994. Manchee, Richard J.; Broster, Malcolm G.; Stagg, Anthony J.; and Hibbs,

Stephen E. “Formaldehyde Solution Effectively Inactivates Spores of Bacillus anthracis on the

Scottish Island of Gruinard.” Applied and Environmental Microbiology, 60: 4167-4171 (1994).

Munro et al., 1999. Munro, Kerry; Lanser, Janice; and Flower, Robert “A Comparative Study

of Methods to Validate Formaldehyde Decontamination of Biological Safety Cabinets.” Applied

and Environmental Microbiology, 65: 873-876 (1999).

NIH, 1979. Laboratory Safety Monograph: A Supplement to the NIH Guidelines for

Recombinant DNA Research. National Institutes of Health, U.S. Department of Health,

Education, and Welfare. Washington, D.C.

NIOSH, 2003. NIOSH Pocket Guide to Chemical Hazards, Publication No. 97-140. U.S.

Department of Health and Human Services. Washington, D.C.

NSF, 2002. NSF/ANSI 49-2002, Annex G. Recommended microbiological decontamination

procedure: Class II (laminar flow) biosafety cabinetry. National Science Foundation and the

American National Standards Institute. Washington, D.C.

SAIC, 2003. Personal communication with Jim Grantham, Certek Inc., Raleigh, NC. August 8,

2003.
167

Taylor et al., 1969. Taylor, Larry A.; Barbeito, Manuel S.; Gremillion, Gardner G.

“Paraformaldehyde for Surface Sterilization and Detoxification.” Applied Microbiolgy, 17: 614-

618 (1969).

USAMRIID, 1999. USAMRIID Regulation 385-17, Decontamination of Containment Areas

with Formaldehyde. U.S. Army Medical Research Institute of Infectious Diseases. Fort Detrick,

MD (February 19,1999).

Wickramanayake, 1990. Wickramanyake, G.B. “Decontamination Technologies for Release

from Bioprocessing Facilities – Part IV: Decontamination of Equipment/ Surfaces.” Critical

Reviews in Environmental Control, 19 (6): 481-513 (1990).
168

5.4 Methyl Bromide 

Methyl bromide is a broad spectrum pesticide. It has been registered under FIFRA as a fumigant

for termites, insects, and rodents in buildings, and as a fumigant for agricultural applications. It

is known to deplete stratospheric ozone, and is being phased out of some of its applications for

that reason.

Methyl bromide, like formaldehyde, appears to function by an alkylation mechanism, rather than

by oxidation (as ClO2 and H2O2 do). It has never previously been registered as a sporicide, but

recent interest in its possible efficacy against B. anthracis (BA) spores has been triggered by the

2001 anthrax mail incident.

 

5.4.1 Description of the Technology 

Following the anthrax mail incident, University of Florida researcher Dr. Rudolf Scheffrahn

proposed the application of methyl bromide for the building remediation of BA spores. Tests

were conducted, with reportedly favorable results, using simulant spore strips in an office-like

setting. A patent application has been filed for the use of methyl bromide as a building fumigant

for bacterial contamination (Scheffrahn, 2002). The patent application is under evaluation.

5.4.2 Technical Maturity

Methyl bromide is fully mature in the applications for which it has been registered (fumigation

of structures for insects and rodents, and soil fumigation). However, it is still in the

experimental stage for use against B. anthracis spores.

5.4.3 Applications of the Technology

Methyl bromide gas is most frequently used as a gas fumigant against termites, rodents and

nematodes. The majority of use in the US (approximately 85 percent) is for pesticide

applications involving soil sterilization (EPA, 2004a). Removal of soil organisms enhances crop

yields. Of those applications, most is used for the cultivation of tomatoes and strawberries. 

Methyl bromide is injected into the soil at a depth of 12-24 inches with the presence of a plastic

vapor barrier on top of the soil to restrict the entry of the gas into the atmosphere. While the

plastic sheeting slows the release of the gas into the atmosphere, it is estimated that the majority

of the gas escapes into the air environment. 

Ten percent of the remaining use is for commodity and quarantine fumigation. Methyl bromide

is also used to decontaminate the exterior of imported produce such as grapes, nuts, cherries, etc. 

When used as such the materials are placed in a tent and the methyl bromide is released into the

tented structure. 

Only five percent of the use is for structural fumigation for rodent and termite control. A

building is tented and methyl bromide is released into the structure. While the methyl bromide is

not very effective against ground resident termites, it is effective against those that reside in the

upper portions of the structure. 
169

Methyl bromide is used in almost all parts of the world. Annual consumption figures for soil

fumigation are provided in Table 5.4-1 (Champon, 2004). The United States is clearly the

largest user of this fumigant. Although these figures are not current (they are from 1996), they

do illustrate a global usage for agriculture.

Table 5.4-1. Global Methyl Bromide Pre-Plant Soil Fumigation: Usage of Methyl Bromide

for Pre-plant Soil Applications by Country (1996)

Country Methyl Bromide

Consumption

(metric tons)

Methyl Bromide

Consumption (lbs.)

United States 15,839 34,908,054

Japan 6,345 13,984,380

Italy 6,000 13,224,000

Israel 2,800 6,171,200

Spain 2,670 5,884,680

France 1,428 3,146,342

Brazil 1,260 2,777,040

Turkey 950 2,093,800

Mexico 900 1,983,600

Zimbabwe 765 1,686,060

Morocco 480 1,057,920

Other 8,461 18,648,044

 Total Pre-plant 47,897 105,565,120

Sources: UNEP, 1995, ICF, 1997.

5.4.4 Evaluation of Available Data

Methyl bromide was reported to be toxic to B. anthracis spores over 50 years ago (Kolb and

Schneiter, 1950). Additional literature reports in the late 1970s by Russian scientists also

documented the ability of methyl bromide to kill BA spores (Pilipenko, 1976; Polyakov et al.,

1976). Chemical methods for spore remediation were well established for laboratory fumigation

(paraformaldehyde) and there was not a pressing need to remediate large structures. Thus this

work appeared to go relatively unnoticed until the terrorist acts of sending BA spores through the

mail. Contamination of buildings with BA spores changed the conventional wisdom and new

methods were sought for large-scale remediation operations. 

Dr. Rudolf Scheffrahn, at the University of Florida, Ft. Lauderdale Research and Education

Center, began evaluation of methyl bromide for bacterial spore inactivation. Dr. Scheffrahn

provided documentation of experiments he conducted or contracted to evaluate the effect of

methyl bromide on bacterial spores (Scheffrahn and Weinberg, 2003). Excerpts from those

documents are included in this section of the report.

Scheffrahn and Weinberg conducted a series of laboratory experiments where they evaluated the

effect of methyl bromide on spores from Bacillus subtilis var. niger (BSN) and Bacillus

stearothermophilus (BST). Spore strips containing either 105

 BST, 106 or 108 BSN were

exposed to methyl bromide. Variables included temperature, time, and concentration of methyl

bromide. After incubation the spore strips were removed from their protective envelopes and
170

transferred into tubes containing growth media, and incubated at the appropriate temperatures for

growth of the respective organisms. If there was no growth after one-week incubation the data

were scored as “pass” if growth was observed, the data were scored as “fail.” Results are

illustrated in Table 5.4-2, which shows the germination of Bacillus stearothermophilus 105

 and

B. subtilis 106 combination spore strips after exposure to methyl bromide in 9-liter glass

chambers under selected concentration, temperature, and time conditions. Each row represents a

single chamber exposure, two strips each.

Table 5.4-2. Spore Germination After Methyl Bromide Exposure

Spore Germination: Pass/Fail 

Exposure Temp MB conc.2 Time Accum. Dose B. stearo. B. subtilis__

Date (oC1

) (mg/L) (hours) (mg-hr/L) strip1 strip2

27Nov01 19 48 63 3,000 fail fail

27Nov01 19 48 104 5,000 fail fail

27Nov01 19 48 146 7,000 fail fail

27Nov01 19 80 112 9,000 pass fail

27Nov01 19 80 134 11,000 pass fail

27Nov01 19 80 164 13,120 pass fail

27Nov01 19 160 164 26,240 pass fail

10Dec01 20 240 48 11,520 nt3 fail

10Dec01 20 320 72 23,040 nt fail

10Dec01 20 320 96 30,720 nt fail

10Dec01 27 240 48 11,520 nt fail

10Dec01 27 320 72 23,040 nt fail pass

10Dec01 27 320 96 30,720 nt pass pass

10Dec01 27 320 96 30,720 nt pass pass4

18Dec01 27 320 48 15,360 nt pass pass

18Dec01 27 320 62 19,776 nt pass pass

18Dec01 32 160 72 11,520 nt fail fail

18Dec01 32 240 48 11,520 nt pass pass 

18Dec01 32 240 72 17,280 nt pass pass 

18Dec01 32 320 38 12,160 nt pass pass 

18Dec01 32 320 47 15,104 nt pass pass 1

 Mean ± 0.4°C.

2

 Theoretical concentration based on MB volume introduced. Actual concentration is lower. Methyl bromide is a

colorless and odorless gas at concentrations harmful or lethal to humans and must be handled with extreme caution by

certified personnel. The American Conference of Government Industrial Hygienists (ACGIH) threshold limit value

(TLV) for human exposure to methyl bromide is 1 ppm (v/v, 8-hour time-weighted average) (equivalent to 0.004

mg/L) (ACGIH, 2002). The concentrations tested here (48 to 320 mg/L) correspond to 12,500 to 80,000 ppm.

3

 nt = not tested. In these tests, both strips were tested for B. subtilis germination. 4

 Chamber contained office commodities listed in text.
171

The results shown in Table 5.4-2 demonstrate temperature dependence for the methyl bromide. 

The data also suggest that the absolute methyl bromide concentration is more important than the

accumulated dose. The data for 18 December for 160 and 240 mg/L (about 40,000 to 60,000

ppm) have the identical accumulated dose but the lower concentration did not kill the spores

even though it has a much longer contact time, 72 verses 48 hours. Most importantly these data

provide documentation that methyl bromide is toxic to bacterial spores in a laboratory setting.

The authors expanded on the initial results by conducting additional exposures using BSN spore

strips containing 108

 spores per strip. These results also documented the temperature, time and

concentration requirements for exhibiting an eight log reduction in spore population. The data

are presented in Table 5.4-3, which shows the germination of Bacillus subtilis 108

 spore strips

after exposure to methyl bromide in 9-liter glass chambers under selected concentration,

temperature, and time conditions. Each row represents a single chamber exposure, two strips

each.

The data presented in Table 5.4-3 indicate that methyl bromide has a killing effect on Bacillus

spores from these two strains. The fact that only two spore strips were used for each condition

prevents statistical evaluation of the results. The fact that one has four variables: temperature,

concentration, time, and total accumulated dose, dictates that more experimentation is required

to critically evaluate the role of these parameters in the effectiveness of the fumigant.

Table 5.4-3. Germination of Spores After Exposure to Methyl Bromide, Second Test

Exposure Temp MB conc. Time Accum. Dose Spore Germination: Pass/Fail

Date (oC) 1 (mg/l) 2 (hours) (mg-hr/l) Strip 1 Strip 2

26Dec01 27.2 320 48 15,360 fail pass

26Dec01 27.2 320 72 23,040 fail pass

26Dec01 27.2 240 48 11,520 fail fail

26Dec01 32.0 320 48 15,360 fail pass

26Dec01 32.0 200 48 9,600 control strip failure

26Dec01 32.0 240 48 11,520 fail pass

26Dec01 32.0 240 72 17,280 fail pass

07Jan02 32.3 320 48 15,360 pass pass

07Jan02 32.3 320 72 23,040 pass pass

07Jan02 32.3 400 48 19,200 pass pass

07Jan02 32.3 400 24 9,600 pass pass

07Jan02 38.3 200 48 9,600 fail pass

07Jan02 38.3 240 48 11,520 pass pass

07Jan02 38.3 320 48 15,360 pass pass

07Jan02 38.3 320 24 7,680 pass pass 

1

 Mean ± 0.4°C.

2

 Theoretical concentration based on MB volume introduced. Actual concentration is lower. Methyl bromide is a

colorless and odorless gas at concentrations harmful or lethal to humans and must be handled with extreme caution

by certified personnel. The threshold limit value (TLV) for human exposure to methyl bromide is 3 ppm (v/v).
172

Figure 5.4-2. Trailer configuration 

As a logical extension of this

preliminary laboratory work, the

authors applied to the U.S. EPA

requesting approval to conduct

fumigation of a trailer into which

spore strips were placed in various

locations. The EPA granted a 15-day

crisis exemption and the results of the

trailer experiment are discussed

below.

Authors Scheffrahn and Weinberg

conducted a well-documented

experiment to evaluate the

effectiveness of methyl bromide in a

household or office setting. The

abstract from the report is presented

in Figure 5.4-1.

Sets of four spore strips were placed

in twenty different locations

throughout the trailer in an attempt to identify areas that would be hard to reach. Illustrations of

some of the placements are shown in Figure 5.4-2. 

A partially furnished 10,000 ft3 mobile home was fumigated

with methyl bromide (MB) after 80 Bacillus spore strips were

placed four each in 20 potential spore contamination sites. A

total of 306.5 lbs of MB was introduced to yield a mean timeweighted concentration of 303.7 oz MB/1,000 ft3

 (about 300

mg/L, or 80,000 ppm) during the 48-hour fumigation. Mean

temperatures near spore strips during fumigation ranged

between 90-95 /F and relative humidity ranged from 39-69

percent. Of the 40 combined B. subtilis 106

 and B.

stearothermophilus 105

 spore strips recovered after the

fumigation, none showed germination and growth. Of the 40

B. subtilis 108

 spore strips placed, only 4 (10 percent) produced

vegetative cells during incubation. During fumigation, 0-2.5

ppm MB was detected downwind from the structure. During

aeration, downwind MB concentrations ranged from 60 ppm at

20 ft to 0 ppm at 150 ft. No damage was detected among the

electronic, photographic, cellulosic, fabric, or other

commodities fumigated. A transient organic odor was detected

up to 7 days after the fumigation. 

Figure 5.4-1. Abstract of Scheffrahn and Weinberg

Study
173

Figure 5.4-4. Spore strip site

13. Left: strips under

mattress.

Right: mattress in place.

Figures 5.4-3 through 5.4-5 show spore strip placements. The trailer was prepared for methyl

bromide fumigation by covering with two tarpaulins that are clamped together and sealed to the

ground with sand “snakes” as shown in Figure 5.4-6. 

Figure 5.4-3. Spore strip sites 1 and 2 (see Table 1). Clockwise from top left: Strips in sub

floor ducting under vent; vent in place. Strips under carpet; carpet in place.
174

Figure 5.4-6. The Prepared Trailer

Figure 5.4-5. Spore strip site 3. Left: strips inside wall insulation. Right: paneling in

place.
175

Figure 5.4-7. Methyl Bromide Concentration During

Trailer Fumigation and Aeration

Methyl bromide was introduced into the trailer and circulated with fans. Heaters were utilized to

keep temperatures elevated. Methyl bromide concentration was monitored, and additional gas

was added when the levels fell below optimal concentration. The profile of methyl bromide

concentration is graphed in Figure 5.4-7. As shown, the average MB concentration during

fumigation was 303.7 oz per 1,000 ft3

 (equivalent to approximately 307 mg/L, or 80,000 ppm).

Following aeration the spore strips were removed and analyzed for growth. The results are

indicated in the table below. Out of 80 spore strips, four demonstrated positive growth. The

four strips that resulted in growth contained 108

 BSN spores. It is important to note that the

higher density spore strips were placed in duplicate. In all cases the duplicate of the spore strip

that demonstrated growth had no growth. These results are consistent with a threshold kill in

these locations. All four of these locations were in hard to reach locations: inside ducting, in a

closed folder on floor, under a mattress, and in a closed closet.

The results of this study suggest that methyl bromide can be an effective fumigant against these

surrogate organisms. The apparent ability of methyl bromide to penetrate porous materials

without discoloration is a very encouraging observation. 

Following these favorable results, the authors requested EPA funding to evaluate methyl

bromide against Bacillus anthracis spores in a laboratory environment. The resulting report is

reprinted in Figure 5.4-8.
176

Table 5.4-4. Spore Strip Location, Proximal Ambient Temperature Conditions, and

Incubation Results for 80 Strips After Exposure for 48 Hours to Methyl Bromide at a

Concentration of 303.7 oz/1,000ft3

 in Trailer

(Pass = No Spore Germination Occurred; Fail = Spore Germination Occurred)

Exposure Temperatures /F 106

 105 B. subtilis 108

Trailer Location No. and Description Mean Max. Min. B. sub. B. stear. Strip A Strip B

1-Floor vent, inside ducting 95.12 98.8 89.6 pass pass pass fail

2-Under carpet fabric 95.12 98.8 89.6 pass pass pass pass

3-Behind wall paneling in insulation 95.12 98.8 89.6 pass pass pass pass

4-Wall plug outlet, covered 95.12 98.8 89.6 pass pass pass pass

5-Wall surface, in closed folder 95.12 98.8 89.6 pass pass pass pass

6-Closed kitchen cabinet 95.07 98.8 89.6 pass pass pass pass

7-PC keyboard, inside back cover 95.07 98.8 89.6 pass pass pass pass

8-PC CD tray, closed 95.07 98.8 89.6 pass pass pass pass

9-Desk drawer, closed 95.07 98.8 89.6 pass pass pass pass

10-Desk drawer, in closed hanging file 95.07 98.8 89.6 pass pass pass pass

11-Ceiling surface, exposed 95.07 98.8 89.6 pass pass pass pass

12-Floor surface, in closed folder 95.07 98.8 89.6 pass pass pass fail

13-Mattress, under box spring 95.07 98.8 89.6 pass pass fail pass

14-Hall closet, closed 90.29 94.1 83.6 pass pass fail pass

15-Medicine cabinet, closed 90.29 94.1 83.6 pass pass pass pass

16-Light fixture, secured globe 90.29 94.1 83.6 pass pass pass pass

17-Central AC inlet, behind filter 90.29 94.1 83.6 pass pass pass pass

18-Window AC, behind filter 93.24 100.2 88.2 pass pass pass pass

19-Under newspapers 93.24 100.2 88.2 pass pass pass pass

20-Recliner chair, under cover fabric 95.12 98.8 89.6 pass pass pass pass

The three sets of experiments by Dr. Scheffrahn summarized above suggest that methyl bromide

may be an effective fumigant against Bacillus spores. The data are consistent and supportive of

further examination into the possibility of using methyl bromide for the remediation of buildings

contaminated with biological materials. (A fourth test in the trailer, utilizing a slightly lower

MB concentration, provided more ambiguous results regarding spore kill, which had not been

explained at the time of this writing; this underscores the need for further testing.)

Little data were found regarding reactivity of methyl bromide with common building elements

such as paints and fabrics. It is reported incompatible with aluminum, dimethyl sulfoxide, strong

acids, strong oxidizers, strong bases, nitrates, and alkaline earth metals according to the

Materials Safety Data Sheet (MSDS). Thus, methyl bromide may affect some materials found in

homes or buildings.
177

The study, IITRI 2050, investigating the disinfectant capabilities of methyl bromide (MB)

against Bacillus anthracis, Bacillus atrophaeus (ATCC 9372, formerly Bacillus subtilis), and

Geobacillus stearothermophilus (ATCC 7953, formerly Bacillus stearothermophilus) spores

is complete. The protocol and results are as follows:

Bacillus anthracis ANR-1 was grown on sporulation media, harvested into deionized water,

heat-shocked, and stored as a spore suspension. The final concentration of this spore

suspension was approximately 1 x 109

 spores/ml. Individual glass coverslips were spiked

with an aliquot (10 ml - ca. 107

 spores) of the spore suspension, which was spread evenly over

the surface and allowed to dry. Two coverslips were placed into each of the experimental

chambers, and three coverslips were placed into the control chamber. In addition, two spore

strips containing G. stearothermophilus (Raven Biological Laboratories, Inc., Omaha, NE)

and one spore strip containing G. stearothermophilus/ B. atrophaeus (Raven Biological Labs)

were placed into each chamber. A damp sponge (1 x 1 x 3-cm) was placed into chambers 1,

3, 5, and 7 to increase the relative humidity. Data loggers were placed in chambers 6 and 7 to

allow monitoring of internal temperature and relative humidity.

Each chamber was sealed so that a minimum of 1 cm unbroken grease seal was visible for the

entire circumference of the chamber. After sealing, the appropriate volume of methyl

bromide (MB) gas was injected into the chambers. The gas was injected using a 100 ml

syringe, and pressure was equalized after each 100 ml of MB added. A fan was run

continually in each chamber during loading, to ensure uniform distribution of the MB over the

entire chamber.

Loaded chambers were incubated at 37 °C (99 °F) for 48 hours. The pressure was equalized 2

hours after placement in the incubator, and the temperature and humidity were monitored

daily. The relative humidity ranged from 21-22 percent in chamber 6 (no sponge) to 92-100

percent in chamber 7 (with sponge). After the 48-hour fumigation, the chambers were

removed from the incubators and vented to allow release of the MB. The B. atrophaeus/

G. stearothermophilus spore strips were removed from their envelopes and placed into

Trypticase Soy Broth containing a colorimetric reagent (Raven Biological Labs). Each B.

anthracis coverslip was placed into a sterile beaker containing 50 ml sterile water and a stir

bar. The coverslips were stirred vigorously for 60 minutes to remove any remaining spores

from the surface. Serial dilutions of the water were made and plated onto Trypticase Soy

Agar. All plates and the B. atrophaeus tubes were incubated for 48 hours at 37 °C, and

counted (plates) or scored for growth/no growth (tubes). The G. stearothermophilus tubes

were incubated for 5 days at 55°C and scored for growth/no growth. The results are seen in

Table 1. 

Figure 5.4-8. Summary of IITRI Research Findings
178

5.4.5 Concerns for the User

Methyl bromide is highly acutely toxic with a TLV of 1 ppm, resulting in degenerative effects of

the nasal cavity and membranes affecting the sense of smell (ACGHI, 2002). The concentrations

of up to 80,000 ppm that must be maintained in a building for 48 hr to fumigate for B. anthracis

are dramatically higher than the TLV. The toxicity is a major consideration at the release points

because it is odorless and colorless at dangerous levels. Accordingly, in building fumigations

using methyl bromide for pest control, about 1% chloropicrin (tear gas) is added as a warning

agent.

The current EPA IRIS classification for methyl bromide is ‘D- not classifiable as to human

carcinogenicity’ (EPA, 2004b). In two-year inhalational carcinogenicity and toxicity studies

conducted in mice by the National Toxicology Program, methyl bromide did not induce tumors

Recovery of viable spores after exposure to methyl bromide.

Accumulated

Dosage

Glass Carriers

Spiked With 

Commercial Spore Strips

Chamber mg-hour/L MB B. anthracis B. atrophaeus G. stearothermophilus AG. stearothermophilus B

1 a 3840 0 growth no growth no growth

2 5760 0 growth no growth no growth

3 a 7680 0 no growth no growth no growth

4 9600 0 no growth no growth no growth

5 a 11520 0 no growth no growth no growth

6b 13440 0 growth no growth growth

7 a,b 15360 0 no growth no growth no growth

10 (control) 0 1.41 x 10 7 growth growth growth

a

 Chambers contain damp sponge.

b

 Chambers contain humidity and temperature logger.

All concentrations of MB tested induced a 6-log or greater reduction in B. anthracis spores. The

limit of detection on this assay is 50 spores per coverslip. The lowest two concentrations of MB

were insufficient to kill all B. atrophaeus spores on a spore strip, but were capable of killing all G.

stearothermophilus spores on a spore strip. Chamber 6 showed some anomalous results. While

lower concentrations of MB were sufficient to disinfect both B. atrophaeus and G.

stearothermophilus in the other chambers, this chamber showed growth for two of the three spore

strips despite the high CT. The reason for this is unclear. Concentrations of MB in the chambers

are computed, not measured during the tests, so perhaps an experimental problem resulted in lower

than expected MB concentrations in Chamber 6. No leaks in the grease seal were observed at the

time of unloading. It is of interest to note that the B. anthracis spores in Chamber 6 were

completely killed.

Figure 5.4-8. Summary of IITRI Research Findings (concluded)
179

in either male or female mice. However, significant neurological effects were noted in mice at

the highest dose (NTP, 1992).

It is estimated that between 50 and 95 percent of the methyl bromide used to fumigate structures

to rid rodents and insects ends up in the atmosphere (EPA, 2004a). Methyl bromide release to

the atmosphere is a serious consideration. Due to the effect of methyl bromide on ozone

depletion, the gas will be phased out for U.S. operations by 2005 as a result of the Clean Air Act

and Montreal Protocol. In spite of the phase out for most commercial applications, the chemical

will still be available for critical agricultural and emergency uses in the U.S. The use of methyl

bromide as a fumigant for biological warfare contamination of a building is considered an

emergency application. 

Methyl bromide is a stable gas and is dispersed into the atmosphere following pesticidal

fumigations. This property is a distinguishing factor from paraformaldehyde, vapor-phase

hydrogen peroxide, and chlorine dioxide, all of which either self decompose or are neutralized

by the introduction of another chemical at the completion of the fumigation.

Venting of highly toxic methyl bromide to the atmosphere is currently legal under current EPAregistered pesticide applications of this product. However, given the large amounts of very highconcentration gas (about 80,000 ppm) that could be present in a building being fumigated for B.

anthracis sterilization, the venting of this building air may raise concerns, especially in densely

populated areas. Given the TLV value of 1 ppm, and given prior experience with the oxidizing

fumigants discussed in the previous chapters, a methyl bromide concentration at the building’s

fence-line would probably need to be maintained at a value below 1 ppm. Unless a reliable

technology is demonstrated for removing methyl bromide from the building air being vented,

and if dilution alone is to be relied upon to protect neighboring populations, a substantial dilution

of the exhaust air would be required to meet the desired fence-line concentrations.

A method of removing methyl bromide from the building air that is vented outdoors is thus

crucial, not only from the standpoint of its ozone-depleting characteristics, but from the

standpoint of the health issues raised above. The absence of a demonstrated approach for

sorbing or otherwise destroying methyl bromide prior to release is a major issue that needs to be

addressed.

5.4.6 Availability of the Technology for Commercial Applications

Methyl bromide is registered by EPA as a pesticide, and is available for commercial applications

as a pesticidal fumigant in buildings and agricultural applications. However, the compound is

not registered as a sporicide. A patent application has been filed in the U.S. for the use of

methyl bromide against bacterial spore contamination in buildings. A final decision regarding

the patent application has not been made. And, as discussed above, additional data appear to be

required before this fumigant could be safely utilized for bacterial sterilization of large buildings.

The application of methyl bromide is relatively straightforward. Monitors for the gas levels,

both inside and outside buildings are commercially available.
180

Methyl bromide is a stable gas. As demonstrated in the trailer test, gas must be added

periodically to structure in order to make up for leakage, demonstrating the need for highly

effective sealing of the enclosure being fumigated. Three additions of approximately fifteen

percent of the original load were required over a forty-eight hour period to compensate for

leakage through and under the tarps over the trailer. The cost of methyl bromide gas is projected

by the developers to be low compared to the cost of generating and distributing chlorine dioxide

or hydrogen peroxide vapor into a structure.

The common practice when using methyl bromide for building fumigation for pest control is to

let the gas vent into the atmosphere. However, if the gas is to be used at concentrations on the

order of 80,000 ppm for treatment of large buildings that must be kept at negative pressure, an

effective means for scrubbing the methyl bromide from the building air before release is critical,

to remove concerns about damage to the ozone layer and potential exposure of humans in the

vicinity.

5.4.7 Advantages and Disadvantages

The main advantage of this technology is that it appears to be effective against Bacillus

anthracis and surrogate bacillus species under conditions that are achievable at a small building

scale. The log kill obtained in laboratory and field trials meets or exceeds the EPA sterilization

requirement. The ability of the gas to penetrate porous surfaces and any cracks or crevices

demonstrates that the gas will reach all locations that a spore could reach. The gas does not

appear to discolor photographs or printed material.

The main disadvantage of methyl bromide is the potential for human exposure to the highly toxic

gas and the potential for ozone layer damage, unless a method can be developed to neutralize or

scrub the methyl bromide from the air that is vented from a structure during and following

fumigation. In addition, 50 to almost 400 time higher concentrations of methyl bromide must be

used to fumigate for B. anthracis, compared to the required concentrations for the other three

fumigants covered in this report, and 4 to 12 times longer contact times are needed.

Methyl bromide is scheduled for phase-out in some of the applications for which it is currently

registered by 2005. However, research is currently continuing into its applicability for anthrax

decontamination in buildings, to determine whether it offers potential (e.g., due to its

penetrability) such that perhaps it should remain available for such emergency applications.

5.4.8 Potential areas for future research

The preliminary data for methyl bromide killing of Bacillus spores suggests potential, but

significant additional efficacy data are required over a range of conditions. In addition, there is a

compelling need for development and demonstration of a means for removal of methyl bromide

from the air exhausted from a building during and after fumigation, to protect people from its

toxic effects and to prevent depletion of the stratospheric ozone layer. Furthermore, rigorous

engineering analysis is required to evaluate the issues involved in scaling up the methyl bromide

fumigation technology, from residential pest-control applications to large-building biological

decontamination applications.
181

Because methyl bromide is a strong alkylating agent, it may be interesting to perform

preliminary studies to evaluate its effect on chemical warfare agents. If methyl bromide is

effective against chemical warfare agents, it might be a candidate for broad spectrum

remediation (addressing both chemical and biological agents).

5.4.9 References

ACGIH, 2002. Threshold Limit Values for Chemical Substances and Physical Agents. 

American Conference of Governmental Industrial Hygienists, Cincinnati, OH.

Champon, 2004. Champon Millennium Chemicals, Inc. Methyl Bromide.

http://www.champon.com/about/metbromide.htm. Accessed December 2004.

EPA, 2004a. U.S. Environmental Protection Agency. Ozone Depletion Rules and Regulations: 

Methyl Bromide Questions & Answers. Available at: 

http://www.epa.gov/docs/ozone/mbr/qa.html. Accessed December 2004.

EPA, 2004b. U.S. Environmental Protection Agency. Integrated Risk Information System: 

Bromomethane (CAS 74-83-9). http://www.epa.gov/iris/subst/0015.htm. Accessed December

2004.

ICF, 1997. “U.S. Methyl Bromide Alternatives Consumption Trends.” Memorandum prepared

for the U.S. Environmental Protection Agency, Stratospheric Protection Division. ICF, Inc.

Washington, DC. January 31, 1996. 

Kolb and Schneiter, 1950. Kolb, R. W.; and Schneiter, R. “The germicidal and sporicidal

efficacy of methyl bromide for Bacillus anthracis.” Journal of Bacteriology, 50: 401-412 (1950).

NTP, 1992. Toxicology and Carcinogenesis Studies of Methyl Bromide (CAS No. 74-83-9) in

B6C3Fi Mice (inhalation studies). National Toxicology Program Report NTP TR 385, National

Institutes of Health Publication No. 92-2840.

Pilipenko, 1976. Pilipenko, A. V. “Disinfection of soil sources of Bacillus anthracis with

methyl bromide.” Vses. Nauchno-Issled. Inst. Vet. Sanit., 54: 138-4 (1976). (In Russian; only

the English abstract was reviewed).

Polyakov et al., 1976. Polyakov, A. A. A.; Kulikovskii, V.; and Pilipenko, A.V. 

“Submicroscopic structure of Bacillus anthracis spores subjected to methyl bromide treatment.” 

Dokl. Vses. Akad. S-kh. Nauk, 12: 23-4 (1976). (In Russian; only the English abstract was

reviewed).

Scheffrahn and Weinberg, 2003. Scheffrahn, Rudolf H.; and Weinberg, Mark J. “Structural

Fumigation with Methyl Bromide for Control of Bacillus Spores: Field Demonstration with B.

subtilis and B. stearothermophilus.” Personal communication with SAIC, July 2003.
182

Scheffrahn, 2002. Scheffrahn, R. H. “Method of Decontamination of Whole Structures and

Articles Contaminated by Pathogenic Spores.” U.S. Patent Application No. 20030129082, filed

March 28, 2002.

UNEP, 1995. 1994 Report of the Methyl Bromide Technical Options Committee, prepared under

Montreal Protocol on Substances that Deplete the Ozone Layer

(http://www.unep.org/ozone/teap/Reports/HTOC/HTOC94.PDF, accessed December 2004). 

United Nations Environment Programme. 
 

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