Destruction of Spores on Building 

Decontamination Residue in a 

Commercial Autoclave

National Homeland Security Research Center

Offi ce of Research and Development

REPORT ON

United States

Environmental Protection

Agency
EPA/600/R-05/081

April 2005

Destruction of Spores on 

Building Decontamination Residue 

in a Commercial Autoclave

by: 

Roy Sieber and Aaron Osborne 

Eastern Research Group, Inc. 

14555 Avion Parkway, Suite 200 

Chantilly, VA 20151 

Dr. Paul Lemieux 

U.S. Environmental Protection Agency 

Office of Research and Development 

National Homeland Security Research Center 

Research Triangle Park, NC 27711 

EP-C-04-056 

Project Officer 

Alice Gagnon 

U.S. Environmental Protection Agency 

Office of Research and Development 

National Risk Management Research Laboratory 

Research Triangle Park, NC 27711 

U.S. Environmental Protection Agency 

Office of Research and Development 

National Homeland Security Research Center 

Decontamination and Consequence Management Division 

Research Triangle Park, NC 27711 
i

NOTICE

 The U.S. Environmental Protection Agency (EPA), through its Office of Research 

and Development, funded this study under Contract Number EP-C-04-056, Work Assignment 0-

7 to Eastern Research Group, Inc. (ERG). This report presents the methodology followed and the 

results of this study to evaluate the effectiveness of a commercial autoclave sterilizing simulated 

building decontamination residue. Simulated building decontamination residue consisting of 

wallboard, ceiling tiles, carpet, and upholstered furniture was prepared with 106

 population 

biological indicator test strips of Geobacillus stearothermophilus. The residue was then 

autoclaved under different conditions to evaluate the influence of the following variables on 

sterilization: time, temperature, pressure, item type, moisture content, packing density, packing 

orientation, autoclave bag integrity, and autoclave process sequence. While the results of this 

study provide valuable data on autoclave performance, this report is not EPA guidance and 

should not be viewed as such. 

 Mention of trade names, products, or services does not convey, and should not be 

interpreted as conveying, official EPA approval, endorsement, or recommendation. 

 This report has been subjected to the Agency’s peer and administrative review 

and has been approved for publication as an EPA document. 
ii

FOREWARD

 The U.S. EPA National Homeland Security Research Center (NHSRC), 

Decontamination and Consequence Management Division (DCMD), one of three divisions of 

NHSRC, is located in Research Triangle Park, North Carolina. The current focus of DCMD is on 

the decontamination of buildings that have been intentionally contaminated with biological or 

chemical agents. DCMD scientists study the biological or chemical contamination of air and 

indoor surfaces; provide methods for upgrading buildings in ways that increase occupant 

protection; supply information on decontamination methods, including safety, efficiency, cost; 

and analyze disposal options for decontamination wastes. 

 This study was conducted as part of the DCMD research goal of evaluating 

commercial decontamination methods and systems. This report is being published to disseminate 

the findings of this study to the potential user community and other interested parties. 

 
iii

ACKNOWLEDGMENTS

 This study was led by Dr. Paul Lemieux, U.S. EPA, Office of Research and 

Development, National Homeland Security Research Center, Decontamination and Consequence 

Management Division. ERG prepared simulated building decontamination residue and conducted 

the autoclave testing. The ERG test team included Roy Sieber, Aaron Osborne, Scott Sholar, 

and Steve Strackbein. Dave Dayton of ERG designed and built the temperature acquisition 

system described herein. Dr. Alan Woodard, New York State Department of Environmental 

Conservation, provided invaluable technical input during the planning and conduct of this study. 

The autoclave test would not have been possible without the facility access, cooperation, and 

technical expertise provided by Healthcare Environmental, Inc. Thank you to Richard Geisser, 

Vice President, Russ Hilton, Plant Manager, and all the dedicated members of the Healthcare 

Environmental team. 
iv

ABSTRACT

 In the event of a terrorist attack on a building where biological weapons such as anthrax 

might be used, much of the porous material in the building will be shipped for disposal after 

decontamination activities. This material is collectively termed “building decontamination 

residue” (BDR). Although the BDR will have been disinfected or decontaminated, it is possible 

that residual biological agent will remain in the material. 

 Autoclaves are commonly used to sterilize regulated medical waste by exposing the 

waste to elevated pressures and temperatures for extended periods of time (e.g., 31.5 psig, 275°F, 

and 40 minutes). However, some types of BDR may be densely packed or have low thermal 

conductivity and may require longer periods of time to reach the operating temperature of an 

autoclave. This report addresses whether the standard operating procedure in a commercial 

autoclave will provide sufficient time/temperature/pressure to adequately destroy bacteria spores 

bound on BDR. 

 This study investigated the effect of several variables related to autoclaving BDR, 

including time, temperature, pressure, item type, moisture content, packing density, packing 

orientation, autoclave bag integrity, and autoclave process sequence. The test team created 

simulated BDR from wallboard, ceiling tiles, carpet, and upholstered furniture, embedded with 

106

 population Geobacillus stearothermophilus biological indicator (BI) strips and 

thermocouples to obtain time/temperature profile data associated with each BI strip. 

 Study results indicate that bags of BDR should be placed in an autoclave so that 

all sides of individual bags are exposed to autoclave conditions, and not nested or stacked in a 

manner that precludes full exposure. All materials tested were effectively sterilized when dry. 

Increasing moisture content made autoclaving more difficult, but wet wallboard and ceiling tiles 

were also effectively sterilized. Autoclave cycles of 120 minutes at 31.5 psig/ 275°F and 75 

minutes at 45 psig/ 292°F effectively sterilized the BDR material. Two standard autoclave cycles 

of 40 minutes and 31.5 psig/ 275°F run in sequence proved to be particularly effective, probably 

because the second cycle’s evacuation step pulled the condensed water out of the pores of the 

materials, allowing effective steam penetration. 
v

TABLE OF CONTENTS

Page 

1.0 INTRODUCTION................................................................................................................ 1-1 

2.0 EXPERIMENTAL APPROACH ............................................................................................. 2-1 

2.1 Autoclave Description ......................................................................................... 2-1 

2.2 Testing Approach................................................................................................. 2-1 

2.3 Test Matrix and Conditions ................................................................................. 2-2 

2.3.1 Item Type.................................................................................................2-3 

2.3.1.1 Wallboard..................................................................................2-6 

2.3.1.2 Ceiling Tiles.............................................................................. 2-7 

2.3.1.3 Carpet........................................................................................2-8 

2.3.1.4 Sofa ......................................................................................... 2-10 

2.3.2 Autoclave Packing Density....................................................................2-10 

2.3.3 Moisture Content ...................................................................................2-11 

2.3.4 Temperature and Pressure......................................................................2-11 

2.3.5 Time .......................................................................................................2-12 

2.3.6 Packing Orientation ...............................................................................2-12 

2.3.7 Open Bags..............................................................................................2-13 

2.3.8 Multiple Short Cycles ............................................................................2-13 

2.4 Test Schedule..................................................................................................... 2-13 

3.0 RESULTS.......................................................................................................................... 3-1 

3.1 Time/Temperature Data....................................................................................... 3-1 

3.2 Biological Indicator Data..................................................................................... 3-1 

3.3 Quality Assurance Data ....................................................................................... 3-2 

3.3.1 Process Measurements.............................................................................3-2 

3.3.2 Experimental Measurements....................................................................3-2 

3.3.2.1 Run Time .................................................................................. 3-2 

3.3.2.2 Temperature ............................................................................ 3-10 

3.3.2.3 Test Conditions ....................................................................... 3-11 

3.3.2.4 BI Test Strip Results ...............................................................3-11 

4.0 DISCUSSION..................................................................................................................... 4-1 

4.1 Time and Temperature Effect on Sterilization..................................................... 4-1 

4.2 Item Type and Moisture Content ......................................................................... 4-2 

4.3 Autoclave Packing Density and Location............................................................ 4-3 

4.4 Temperature and Pressure.................................................................................... 4-5 

4.5 Packing Orientation ............................................................................................. 4-5 

4.6 Open Bags............................................................................................................ 4-6 

4.7 Two Sequential Cycles ........................................................................................4-6 

5.0 CONCLUSIONS ................................................................................................................. 5-1 

6.0 REFERENCES.................................................................................................................... 6-1 

Appendix A PHOTOGRAPHIC LOG 
vi

LIST OF TABLES 

Page

Table 2-1. Originally Planned Healthcare Environmental Autoclave Test Matrix .................... 2-4 

Table 2-2. Healthcare Environmental Autoclave Test Matrix as Completed............................. 2-5 

Table 3-1. Biological Indicator Data .......................................................................................... 3-3 
vii

LIST OF FIGURES 

Page 

Figure 2-1. Side View Sketch of Dense Packing Arrangement.................................................. 2-7 

Figure 2-2. Configuration of Sample Points in a Large Carpet Roll ........................................ 2-10 

Figure 3-1. Run 1 Time/Temperature Data............................................................................... 3-13 

Figure 3-3. Run 4 Time/Temperature Data............................................................................... 3-15 

Figure 3-4. Run 8 Time/Temperature Data............................................................................... 3-16 

Figure 3-5. Run 5 Time/Temperature Data............................................................................... 3-17 

Figure 3-6. Run 6 Time/Temperature Data............................................................................... 3-18 

Figure 4-1. Run 2 Spore Viability............................................................................................... 4-8 

Figure 4-2. Run 4 Spore Viability............................................................................................... 4-9 

Figure 4-3. Run 5 Spore Viability............................................................................................. 4-10 

Figure 4-4. Run 1 Moisture Content and Item Type Comparison ............................................ 4-11 

Figure 4-5. Run 8 Moisture Content and Item Type Comparison ............................................ 4-12 

Figure 4-6. Run 5 Moisture Content and Item Type Comparison (Uncut Bags Only)............. 4-13 

Figure 4-7. Run 6 Moisture Content and Item Type Comparison ............................................ 4-14 

Figure 4-8. Wallboard Packing Density Comparison............................................................... 4-15 

Figure 4-9. Carpet Packing Density Comparison ..................................................................... 4-16 

Figure 4-10. Run 2 Dense Packing Layer Comparison ............................................................ 4-17 

Figure 4-11. Comparison of Sampling Points within Selected Wallboard Bags...................... 4-18 

Figure 4-12. Comparison of Sampling Points within Selected Ceiling Tile Bags.................... 4-19 

Figure 4-13. Autoclave Temperature Comparison for Wallboard............................................ 4-20 

Figure 4-14. Autoclave Temperature Comparison for Ceiling Tiles........................................ 4-21 

Figure 4-15. Horizontal Versus Vertical Packing Orientation for Wallboard.......................... 4-22 
viii

Figure 4-16. Horizontal Versus Vertical Packing Orientation for Ceiling Tiles ...................... 4-23 

Figure 4-17. Horizontal Versus Vertical Packing Orientation for Carpet ................................ 4-24 

Figure 4-18. Cut Versus Uncut Wallboard Bags ...................................................................... 4-25 

Figure 4-19. Cut Versus Uncut Ceiling Tile Bags.................................................................... 4-26 

Figure 4-20. Cut Versus Uncut Carpet Bags ............................................................................ 4-27 
 1-1

1.0 INTRODUCTION

 In the event of a terrorist attack on a building where biological weapons (BW) 

such as anthrax might be used, much of the porous material in the building will be shipped for 

disposal after decontamination activities. These materials are collectively termed “building 

decontamination residue” (BDR). Although the BDR will have been disinfected or 

decontaminated, it is possible that residual BW agent will remain in the material. Many of these 

materials might be tightly packed and possibly wet. Autoclaves are commonly used to 

effectively treat regulated medical waste by exposing the waste to elevated pressures and 

temperatures for extended periods of time (e.g., 31.5 psig, 275°F, and 40 minutes at the test 

facility). However, BDR has low thermal conductivity and may require more time to reach the 

operating temperature of an autoclave. 

 It is unknown whether the standard operating procedure in a commercial 

autoclave will provide sufficient time/temperature/pressure to adequately destroy bacteria spores 

bound on BDR. The primary objective of this study was to determine what recommended 

operating conditions at a commercial medical waste autoclave are sufficient to destroy bacteria 

spores found on BDR. The secondary objective of this study was to investigate the 

time/temperature dependence of Geobacillus stearothermophilus spore destruction as a function 

of autoclove operating conditions and BDR composition. The commercial autoclave tested is 

operated by Healthcare Environmental, Inc., in Oneonta, NY. Viability of bacteria spores was 

tested using 106

 population biological indicator (BI) strips of viable spores of Geobacillus 

stearothermophilus, embedded in the materials processed by the autoclave. BDR materials 

tested included carpeting, wallboard, and ceiling tiles, both dry and wetted with water. 

Additionally, a sofa was processed to test the efficacy of autoclaving upholstered furniture. 

 This study was performed according to an approved Quality Assurance Project 

Pla (QAPP), Destruction of Spores on Building Decontamination Residue in a Commercial 

Autoclave (1). 
 2-1

2.0 EXPERIMENTAL APPROACH 

2.1 Autoclave Description

This test was conducted at the Healthcare Environmental, Inc. facility located in 

Oneonta, Oswego County, approximately 90 miles from Albany, New York. The facility 

operates a permitted, regulated medical waste autoclave process with approximately 84 tons/day 

(TPD) capacity. The facility has two large autoclaves 8 feet in diameter and 32 feet long, which 

accept large bins (80 inches by 54 inches by 69 inches) on rollers. Each autoclave can process 6 

bins, with a total mass of approximately 3,000-4,000 pounds per cycle. Photographs 17 through 

20 show the autoclave configuration. All photographs of the test are provided in Appendix A to 

this report. 

 The nominal autoclave operating cycle time is 40 minutes plus cool-down time to 

prepare for subsequent charges. At the start of each cycle, the autoclave is sealed and air is 

evacuated for 3 minutes using a vacuum pump to approximately -10 psig. Steam is then injected 

to reach and maintain the desired operating pressure and temperature, which are typically 

achieved in approximately 5 minutes. The nominal operating conditions during the cycles are 

31.5 psig and 275°F. Steam is injected through three ports at the top of the autoclave, located at 

the front, center and rear. The steam is injected over distributor plates to cause turbulent, 

disbursed steam flow throughout the autoclave. At the end of each cycle, steam is evacuated by 

again pulling vacuum. Both autoclave units are identical. The facility continuously measures 

the operating temperature and pressure within each autoclave unit using a digital readout and 

paper chart recorder. 

2.2 Testing Approach

 Autoclave performance was judged based on two parameters: real-time 

measurements from thermocouples embedded in each simulated load of BDR material tested and 

viability of 106 Geobacillus stearothermophilus BI test strips embedded within each load tested. 

The testing comprised a series of test runs at different conditions on one of the facility autoclaves 

(Unit A1). Section 2.3 discusses the conditions tested. 
 2-2

 

 For each test run, the BDR material processed was wired with 24 thermocouples 

to record the time/temperature profile at different locations embedded within the load. A BI 

pouch was paired with a thermocouple at each test location. Each BI pouch contained two 

Geobacillus stearothermophilus indicator strips, labeled ‘A’ and ‘B’. After the test, the A strips 

were analyzed for a growth/no-growth indication, and a population assay was performed on the 

B strips if the A strips grew, as discussed in Section 3.2. Additionally, control thermocouples 

not embedded in BDR recorded the temperature inside and outside the autoclave. Three types of 

control BI test pouches, further explained in Section 3.3.2.4, were also collected: BI test pouches 

fully exposed to the autoclave conditions, BI test pouches packaged and handled similarly to 

other BDR but not autoclaved, and duplicate BI test pouches. 

2.3 Test Matrix and Conditions

 As discussed in the QAPP, the following variables were identified as having a 

potential impact on sterilization capability: 

1. Item type; 

2. Autoclave packing density (i.e., loose packing versus dense packing); 

3. Moisture content of autoclaved materials; 

4. Autoclave temperature/pressure; and 

5. Time in autoclave. 

 The test matrix presented in Table 2-1 was designed to investigate the effects of 

each of these variables. 

 Temperature data from initial test runs indicated that internal temperatures of 

densely packed material responded slowly to autoclave conditions, and therefore, this material 

was not likely being sterilized after 120 minutes, the maximum autoclave run time established 

for the test. After discussion among the EPA Work Assignment Manager (WAM), ERG WAM, 

New York State Department of Environmental Conservation (NYSDEC) representative, and the 

autoclave facility manager, originally planned Runs 2, 5, 6, and 7 were deleted and three 
 2-3

additional factors were identified and tested to determine if they improved sterilization 

capability: 

1. Positioning sample bags of BDR vertically instead of horizontally; 

2. Cutting open the bags of BDR to facilitate steam penetration; and 

3. Running two shorter process cycles in sequence instead of one long cycle. 

 A revised test matrix was developed based on the temperature results of the initial 

runs and the objective of testing additional factors to improve sterilization. The changes to the 

test matrix were based partially on altering test conditions within easily adjusted facility 

operating constraints. Table 2-2 presents the revised test matrix. All run numbers discussed in 

this document are the revised test matrix run numbers. Run numbers were assigned based on the 

set of prenumbered thermocouples and corresponding BDR used in the run. Runs are typically 

discussed in the order in which they were conducted: 1, 2, 4, 8, 5, 6. Each variable tested is 

discussed in further detail below. 

2.3.1 Item Type 

 The BDR tested included 1⁄2-inch thick, 4 feet by 8 feet sheets of LaFarge regular 

grade drywall (wallboard), e-inch thick, 2 feet by 4 feet Armstrong Contractor Series Ceiling 

Panels Model #942 (ceiling tiles), and Mannington Nepenthe II Blue commercial grade carpeting 

(Nylon 6,6 fibers). New, unused wallboard and ceiling tiles were purchased from a building 

material supplier. Used commercial carpeting, in rolls of varying sizes, was obtained from a 

carpet installation contractor. Additionally, a used queen-sized sleeper sofa was obtained from a 

thrift store. 

 Test material was cut up and packaged to simulate likely BDR generated from a 

building decontamination scenario. Decontamination personnel are expected to size BDR to be 

easily handled and pack it for shipment using a double-bagging technique. The techniques used 

are similar to those from the State Department Sterling, Virginia mail facility anthrax cleanup 

(2). The steps used to reduce the size and package each of these items are discussed below. 
Table 2-1. Originally Planned Healthcare Environmental Autoclave Test Matrix 

Run Item Type

Temp/ 

pressure Time Position/Bin 1 Position/Bin 2 Position/Bin 3 Position/Bin 4 Position/Bin 5 

1 Mixed, loose pack 275°F/ 

31.5 psig 

Thermal Mass (~700lbs) 

Loose Pack CT, Dry WB, Dry ~250 lbs (10 TC) 

Loose Pack CT, Wet WB, Wet ~300 lbs (10 TC) 

Thermal Mass (~700 lbs) 

Carpet, small rolls, dry (4 TC) 

LoobagSteof a

2 Wallboard, dense 

pack 

275°F/ 31.5 psig 

Thermal Mass (~700lbs) 

Dense Pack WB, Dry ~700 lbs (12 TC) 

Dense Pack WB, Wet ~850 lbs (12 TC) 

Thermal Mass (~700 lbs) 

Open Sim

appbag

3 Wallboard, dense 

pack 

292°F/ 45 psig 

Thermal Mass (~700lbs) 

Dense Pack WB, Dry ~700 lbs (12 TC) 

Dense Pack WB, Wet ~850 lbs (12 TC) 

Thermal Mass (~700 lbs) 

Open Sim

to u

4 Carpet Select based 

on runs 1, 2, 3 

Thermal Mass (~700lbs) 

Small rolls, loose pack, wet and dry ~250 lbs (8 TC) 

Small rolls, dense pack wet and dry ~700 lbs (8 TC) 

Large roll, wet (8 TC) Tes

witvar

5 Ceiling tiles, 

dense pack 

275°F/ 31.5 psig 

Thermal Mass (~700lbs) 

Dense Pack CT, Dry ~700 lbs (12 TC) 

Dense Pack CT, Wet ~850 lbs (12 TC) 

Thermal Mass (~700 lbs) 

Open Sim

wa

6 Ceiling tiles, 

dense pack 

292°F/ 45 psig 

Thermal Mass (~700lbs) 

Dense Pack CT, Dry ~700 lbs (12 TC) 

Dense Pack CT, Wet ~850 lbs (12 TC) 

Thermal Mass (~700 lbs) 

Open Sim

upp

7 Carpet Select based 

on prior runs 

Thermal Mass (~700lbs) 

Small rolls, loose pack, wet and dry ~250 lbs (8 TC) 

Small rolls, dense pack wet and dry ~700 lbs (8 TC) 

Large roll, wet (8 TC) Tes

witvar

8 Mixed, loose pack 292°F/ 

45 psig 

Target time at 250°F (121°C) for 

all thermocouples is 15 minutes. Provide a minimum run time of 40 minutes. Extend run time as needed to achieve temperature targets. 

Thermal Mass (~700lbs) 

Loose Pack CT, Dry WB, Dry ~250 lbs (10 TC) 

Loose Pack CT, Wet WB, Wet ~300 lbs (10TC) 

Sofa (4 TC) Sim

 (x TC) designates “x” thermocouples per bin. WB = Wallboard. CT = Ceiling Tile. CP = Carpet. 

2-4
Table 2-2. Healthcare Environmental Autoclave Test Matrix as Completed 

Run

Original 

Matrix 

Run Item Type

Temp/ 

pressure Time Position/Bin 1 Position/Bin 2 Position/Bin 3 Position/Bin 4 Position/Bin 5 

1 1 Mixed, loose 

pack 

275°F / 

31.5 psig 

120 min Thermal Mass 

(~800lbs) 

Loose Pack WB, Wet and Dry ~215 lbs (10 TC) 

Loose Pack CT, Wet and Dry ~170 lbs (10 TC) 

Carpet, small rolls, dry ~150 lbs (4 TC) 

Thermal Mass (~800 lbs) 

One leSteam all bagof time

2 3 Wallboard, 

dense pack 

292°F / 

45 psig 

120 min Thermal Mass 

(~800lbs) 

Dense Pack WB, Wet ~850 lbs (12 TC) 

Dense Pack WB, Dry ~750 lbs (12 TC) 

Thermal Mass (~800 lbs) 

Open Went d

origina

heating 

4 4 Carpet 275°F / 

31.5 psig 

120 min Thermal Mass 

(~800lbs) 

Small rolls, dense pack, wet and dry ~250 lbs (8 TC) 

Small rolls, loose pack wet and dry ~850 lbs (8 TC) 

Large roll, wet (8 TC) Test pa

carpet within 

8 8 Mixed, loose 

pack 

292°F / 

45 psig 

75 min Thermal Mass 

(~800lbs) 

Loose Pack WB, Wet and Dry ~215 lbs (10 TC) 

Loose Pack CT, Wet and Dry ~170 lbs (10 TC) 

Sofa (4 TC) Similar 

time wconcerabove potenti

5 Not 

Included 

Mixed, loose vertical pack 

275°F / 31.5 psig 

2 cycles each 40 min 

Thermal Mass (~800lbs) 

Vertical Pack CT, Wet and Dry CP, Wet and Dry ~125 lbs (12 TC) 

Vertical Pack CT, Wet and Dry WB, Wet and Dry ~125 lbs (12 TC) 

Thermal Mass (~800 lbs) 

Open Test to 

sequen

6 Not 

Included 

Mixed, loose vertical pack 

275°F / 31.5 psig 

2 cycles each 40 min 

Thermal Mass (~800lbs) 

Vertical Pack CT, Wet and Dry CP, Wet and Dry ~125 lbs (12 TC) 

Vertical Pack CT, Wet and Dry WB, Wet and Dry ~125 lbs (12 TC) 

Thermal Mass (~800 lbs) 

Open Similar 

 (x TC) designates “x” thermocouples per bin. WB = Wallboard. CT = Ceiling Tile. CP = Carpet. 

2-5
 2-6

2.3.1.1 Wallboard 

The wallboard was cut into approximately 2 feet by 2 feet sections as described in 

the QAPP. Sample BDR bags were formed by placing five, 2 feet by 2 feet sections face to face 

in autoclave bags. Samples requiring wetting were submerged in tank of water for 30 seconds 

and placed on a drain rack for 5 minutes prior to being placed in the bag. Dry test bags weighed 

approximately 34 pounds, and wet bags weighed approximately 37 pounds. Samples were 

double bagged in 1.8 mil polypropylene autoclave bags, and the bags were individually goosenecked and taped shut using duct tape. A section of nylon rope was attached to the gooseneck to 

allow ERG personnel to easily and safely load and unload the bags from the autoclave bins. 

 Three types of wallboard bags were created. Some test bags were assembled 

with one thermocouple and one test strip pouch placed together, between the second and third 

wallboard section. These are referred to as “1-sample” bags. Other test bags were assembled 

with three thermocouples paired with three test strip pouches placed between the first and 

second, second and third, and fourth and fifth wallboard sections. These are referred to as “3-

sample” bags. Photographs 2 through 8 in Appendix A show how the bags were assembled. 

Additional bags were made without thermocouples and BI test pouches to be used as fillers when 

packing the autoclave bins. 

 Bags were placed in the autoclave bins in either a loose packing or dense packing 

arrangement as indicated on the test matrix in Table 2.2. In the loose packing arrangement, six 

bags were placed per bin: two 3-sample bags and four 1-sample bags. Ten total samples were 

collected per bin in loose density packing. See Photograph 27 for the loose packing arrangement 

of wallboard bags. 

 In the dense-packing arrangement, 23 bags were placed in each bin including 

three, 3-sample bags and three 1-sample bags. The remaining 17 bags were used to fill out the 

load. Bags were layered within the bin, in approximately three to four layers of four to six bags 

each. Bags were placed in the bin with one 3-sample and one 1-sample bag in each layer, so that 

sample bags were dispersed throughout the loaded bin. Twelve total samples were collected per 
 2-7

bin in the dense packing arrangement. See the side view sketch in Figure 2-1 and Photograph 29 

dense packing arrangement of bags. 

 For the vertical packing arrangement, one dry 3-sample and one wet 3-sample bag 

were placed in a bin. Ropes tied to opposite edges of the autoclave bin wall were used to 

maintain the vertical alignment, as shown in Photograph 35. 

Figure 2-1. Side View Sketch of Dense Packing Arrangement 

2.3.1.2 Ceiling Tiles 

 Ceiling tiles were cut into approximately 2 feet by 2 feet sections as described in 

the QAPP. Samples were prepared similarly to wallboard; however, bags contained nine 2 feet 

by 2 feet sections placed face to face. Dry test bags weighed approximately 23 pounds, and wet 

bags weighed approximately 31 pounds. 
2-8

 One-sample bags contained one thermocouple and one test strip pouch placed 

together, between the fourth and fifth ceiling tile section. Three-sample bags contained three 

thermocouples paired with three test strip pouches placed between the second and third, fourth 

and fifth, and seventh and eighth ceiling tile sections. Additional bags were made without 

thermocouples and BI test pouches to be used as fillers. 

 As discussed previously, originally planned runs of densely packed ceiling tiles 

were deleted from the test matrix. In the loose packing arrangement, two 3-sample bags and four 

1-sample bags were placed per bin. Ten total samples were collected per bin in loose density 

packing. See the Photograph 30 for the loose packing arrangement of bags. 

 For the vertical packing arrangement, one dry 3-sample and one wet 3-sample bag 

were placed in a bin. Ropes tied to opposite edges of the autoclave bin wall were used to 

maintain the vertical alignment, as shown in Photograph 35. 

2.3.1.3 Carpet 

 Carpet was tested in two general configurations, small and large rolls. For small 

rolls, the contractor cut the carpet into strips 26 inches wide by 20 feet long, representing how 

carpet would most likely be removed from a building. Samples requiring wetting were soaked 

with a hose-end sprayer. After wetting, samples were rolled and placed on end to allow freeflowing water to drain. Small rolls were bagged in a similar manner to wallboard and ceiling 

tiles. Dry test bags weighed approximately 26 pounds, and wet bags weighed approximately 40 

pounds. As a worst case, larger sections of carpet 6 feet wide and 24 feet long also were 

requested and obtained from the contractor. Large rolls were only prepared wet, and weighed 

approximately 200 pounds, which represented the maximum size that could be handled by two 

workers. Large rolls were wrapped in polypropylene and all seams sealed with duct tape. 

Photographs 10 through 15 in Appendix A show the assembly process for carpet bags. 

 For the small carpet rolls, 1- and 3-sample bags were prepared. One-sample bags 

contained one thermocouple and one test strip pouch placed together, at the approximate midpoint of the radius of the carpet roll. Three-sample bags contained three thermocouples paired 
2-9

with three test strip pouches placed two laps in from the top, at the mid-point of the radius, and 

two laps from the center of the carpet roll. Additional bags were made without thermocouples 

and BI test pouches to be used as fillers. 

 Bags with small rolls of carpet were placed in the autoclave bins in either a loose 

packing or dense packing arrangement. In the loose packing arrangement, two, 3-sample bags 

and two, 1-sample bags were placed in a bin. Bags that did not contain sample points were used 

to fill out the load. Eight total samples were collected per bin in the loose packing arrangement. 

 In the dense packing arrangement, shown in Photograph 33, 25 bags were placed 

per bin including two 3-sample bags and two 1-sample bags. The remaining 21 bags were used 

to fill out the load. Bags were layered within the bin, in approximately three to four layers of six 

to eight bags each. Bags were placed in the bin so that two 3-sample bags were placed in the 

middle layer and two 1-sample bags were placed in the bottom layer. Eight total samples were 

collected per bin in the dense packing arrangement. 

 For the vertical packing arrangement, one dry 3-sample and one wet 3-sample bag 

were placed in a bin. Ropes tied to opposite edges of the autoclave bin wall were used to 

maintain the vertical alignment, as shown in Photograph 35. 

 The large roll of carpet was assembled with eight thermocouples paired with eight 

test strip pouches placed at eight locations throughout the roll. The locations were arrayed 

progressively deeper within the rolled carpet, as depicted in Figure 2-2. The large roll of carpet 

was placed in the autoclave on a wood pallet rather than in a bin, as shown in Photograph 34. 
2-10

Figure 2-2. Configuration of Sample Points in a Large Carpet Roll 

2.3.1.4 Sofa 

 A used queen-sized sleeper sofa was obtained from a thrift store and autoclaved in 

Run 4. The sofa was not wetted prior to being autoclaved. Four thermocouple and test strip 

pouches were paired and embedded in different locations in the sofa. Samples were inserted in 

holes cut approximately 6 inches deep in a back cushion and a seat cushion. The holes were then 

covered with duct tape. One sample was also placed in between the folded sleeper mattress, and 

one in between the seat cushions. The sofa was wrapped in polypropylene and all seams sealed 

with duct tape, as shown in Photograph 16. The sofa was placed in the autoclave on a sheet of 

plywood. 

2.3.2 Autoclave Packing Density 

 The Healthcare Environmental autoclave is designed to operate with six loaded 

bins of material, loaded with approximately 700 pounds of material each. 

 Wallboard was tested at two different bin packing densities. Low density packing 

involved placing six bags in a bin. In a low density arrangement, shown in Photograph 27, the 
2-11

bags formed a single layer at the base of the bin, and all bag surfaces were readily exposed to 

autoclave temperatures. High density packing, shown in Photograph 29, involved placing 23 

bags in each bin. The bags were layered approximately three to four levels deep, exposing some 

bags directly to autoclave conditions while others were buried within the load in the bin. Ceiling 

tiles were only tested in a low density arrangement, as described above for wallboard. Runs of 

densely packed ceiling tiles were deleted from the test matrix because densely packed BDR 

material could not be brought up to autoclave temperatures within the 120-minute duration 

specified in the test plan. 

 Carpet was tested in three configurations. Small rolls, approximately 1 foot in 

diameter and 26 inches long, were placed in bags. Six bags were placed in a bin for low density 

packing, as above (see Photograph 31). Twenty-five bags were placed in a bin for high density 

packing, as above (see Photograph 33). In addition, the effect of the autoclave on a large, intact 

roll of carpet 6 feet long and approximately 1.5 feet in diameter, shown in Photograph 34, was 

tested in Run 4. 

2.3.3 Moisture Content 

 Materials were tested both dry and wet. In this context, dry means in as-is 

condition at ambient humidity, with no additional moisture added. Wet conditions were created 

by briefly immersing wallboard and ceiling tile pieces in water and allowing them to drain. 

Immediately after draining, the wallboard and ceiling tiles were placed in sealed polyethylene 

bags. Carpet was soaked with a hose-end sprayer until saturated, and then allowed to drain. 

After draining, carpet pieces were rolled up and sealed in either polyethylene bags (small rolls) 

or wrapped in polyethylene sheeting (large rolls). Wet and dry bags of BDR were weighed to 

determine the additional water weight. On average, wetting increased the weight of wallboard 

bags by 9 percent, ceiling tile bags by 34 percent, and carpet bags by 53 percent. 

2.3.4 Temperature and Pressure 

 Temperature and pressure are related variables, as the autoclave is designed to 

operate at saturated steam conditions. The study investigated two conditions: 31.5 psig / 275°F, 
2-12

the typical operating pressure of the autoclave, and 45 psig / 292°F, the maximum operating 

pressure of the autoclave. Pressure is the parameter controlled by the autoclave controller. 

These temperatures and pressures are as measured in the interior space of the autoclave. 

Temperatures within the autoclaved items lagged behind these temperatures, as discussed in 

Section 2.3.5. 

2.3.5 Time 

 A minimum run time of 40 minutes at elevated temperature was established, 

according to standard operation of the Healthcare Environmental autoclave. Literature data 

indicate that 15 minutes at 250°F is required for assured moist heat sterilization (3,4). Therefore, 

the test plan called for extending the run time beyond 40 minutes to achieve a 250°F temperature 

target at all, or at least most embedded thermocouples. Even if the 250°F target had not been 

achieved, the test plan established a maximum run time of 120 minutes to enable the autoclave to 

process multiple test runs each day. Runs 1, 2, and 4 were terminated after 120 minutes, prior to 

all thermocouples reaching the target temperature. Run 8 was stopped after 75 minutes due to 

concerns that the sofa temperature was rising above the temperature of the autoclave, indicating 

a potential exothermic reaction in the sofa. Because such a reaction and possible associated 

hazards were not well understood, the run was terminated. Conducting two 40-minute runs in 

sequence was investigated in Runs 5 and 6. This variation is discussed further in Section 2.3.8. 

2.3.6 Packing Orientation 

 Material was tested both lying horizontally in the autoclave bins and positioned 

vertically, with all sides exposed. Material was positioned vertically by tying two ropes to the 

top of the bag and attaching the ends of the rope to opposite sides of the autoclave bin wall, as 

shown in Photograph 35. This packing orientation was introduced as a test variable to simulate 

using a rack system to position bags so that all sides are exposed to autoclave steam. We 

theorized that vertical orientation of the BDR would reduce compression from its own weight, 

and also would allow steam condensate to drain more easily as it formed. If these theories are 

correct, both would facilitate steam penetration and improve heating of the material in the 

autoclave. 
2-13

2.3.7 Open Bags 

 All BDR was double-bagged in 1.8 mil polypropylene bags. The bags were 

individually goose-necked and sealed with duct tape. This procedure was adopted based on 

packaging information from the State Department Sterling, Virginia mail facility anthrax cleanup 

(2). After autoclaving, some of the bags had clearly ruptured due to temperature and pressure 

changes. However, in many cases bag surfaces bubbled and became deformed in the autoclave, 

but it was not clear if they had fully opened. To test if the bags opening had an effect on 

sterilization, two bags in Run 5 and all of the bags in Run 6 were opened prior to autoclaving, by 

slicing two sides of each bag open with a utility knife across their entire length. 

2.3.8 Multiple Short Cycles 

 As steam in the autoclave was evacuated to end Runs 2, 4, and 8, the test team 

observed that, as the vacuum was drawn, most thermocouple readings converged toward a midpoint temperature. Not only were high readings falling, but most of the lower readings were 

rising and converged together. It is not known if this was a result of increased turbulence during 

the post-vacuum cycle, condensed water being drawn out of BDR under vacuum, or some 

combination of these and other factors. However, in consultation with EPA WAM, we decided 

that it would be worthwhile to further investigate this phenomenon. Therefore, in Runs 5 and 6, 

two complete normal autoclave operating cycles were run in succession. Each cycle consisted of 

a pre-vacuum, steam pressurization, and post-vacuum phase. The cycles were conducted in 

immediate succession and the autoclave remained sealed throughout both cycles. 

2.4 Test Schedule

ERG conducted BDR size reduction, wetting, sample placement, and packaging at 

its Chantilly, Virginia facility between February 15 and February 24, 2005. Materials were 

stored at room temperature until March 1, 2005. 
2-14

 Materials were placed on truck trailers on March 1, 2005 and transported to 

Oneonta, New York by Roadway Express, Inc. Trailers were delivered in Oneonta on March 3, 

2004. ERG sealed the trailers in Chantilly, and broke the seals in Oneonta. 

 Test materials were unloaded and staged for processing on March 4, 2005, and 

autoclaved on March 5 and 6, 2005. 
 3-1

3.0 RESULTS

 This section presents the time/temperature, biological indicator, and quality 

assurance data collected during this test. Section 4 presents the analysis of the data. 

3.1 Time/Temperature Data

 Real-time temperature measurements were monitored and recorded at each 

sampling point using a GEC Instruments Model S27TC temperature measurement system and 

Type “T” thermocouples. Figures 3-1 through 3-6 (located at the end of this section) present 

plots of the time/temperature data recorded during each of the six runs. Temperature data were 

recorded at each location approximately every 10 seconds. The figures also include readings 

from the control thermocouple inside the autoclave, the reference thermocouple outside the 

autoclave, and the autoclave set point pressure/temperature. Note that Figures 3-1 through 3-6 

are designed to present an overview of all time/temperature data associated with each run. 

Section 4.0 provides further analysis of these data and distinction between the variables. 

 The facility monitoring system collected additional process measurement data. 

Operating temperature and pressure within the autoclave were measured using the existing 

autoclave thermocouple and pressure gauge and synchronized against 24-hour clock time. The 

time, temperature, and pressure were recorded during the test on a 24-hour circular chart 

recorder. 

3.2 Biological Indicator Data

 A BI test pouch, containing two BI test strips, was placed at each sampling point. 

Each BI strip contained a 106

 population of Geobacillus stearothermophilus on Schleicher & 

Schuell filter paper (#470) encased in a glassine peel-open envelope. The test pouch consisted of 

medical grade paper with a plastic facing. Raven Biological Laboratories, Inc. (Raven) provided 

the BI pouches (American Type Culture Collection #7953, Lot #3167091, expiration January 

2007). The strips within each pouch were designated ‘A’ strips and ‘B’ strips. Following the 

test, Raven cultured all A strips for an indication of growth or no-growth. For A strips indicating 
 3-2

growth, Raven performed a population assay of the B strip to quantify the survivor population. 

Table 3-1 presents the results from these analyses. 

3.3 Quality Assurance Data

 This section presents quality assurance data collected and compares all data 

collected with the acceptance criteria presented in Section 7.0 of the QAPP. 

3.3.1 Process Measurements 

 Autoclave temperature, autoclave pressure, and run time were recorded on a 24-

hour circular chart recorder. Record data where accurate to the following levels, meeting the 

acceptance criteria: 

• Autoclave temperature: ± 5°F 

• Autoclave pressure: ± 0.5 psig 

• Run time: ± 1 minute 

3.3.2 Experimental Measurements 

 Quality data for each of the experimental measurements are presented in the 

following subsections. 

3.3.2.1 Run Time 

 The temperature logging system was synchronized to ± 1 minute with the 

autoclave data recorder clock at the beginning of each day. All time/temperature data was time 

stamped to ± 1 second. All data was time stamped and therefore is considered usable. 
Table 3-1. Biological Indicator Data 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

1 101 WB D B Loose Pack - Horizontal 79 1 101 WB D B Loose Pack - Horizontal 80 Duplicate 1 102 WB D B Loose Pack - Horizontal 81 1 103 WB D B Loose Pack - Horizontal 82 1 104 WB D B Loose Pack - Horizontal 83 1 105 WB D B Loose Pack - Horizontal 84 1 106 CT D B Loose Pack - Horizontal 85 1 107 CT D B Loose Pack - Horizontal 86 1 108 CT D B Loose Pack - Horizontal 87 1 109 CT D B Loose Pack - Horizontal 88 1 110 CT D B Loose Pack - Horizontal 89 1 111 WB W B Loose Pack - Horizontal 90 1 112 WB W B Loose Pack - Horizontal 91 1 113 WB W B Loose Pack - Horizontal 92 1 114 WB W B Loose Pack - Horizontal 93 1 115 WB W B Loose Pack - Horizontal 94 1 115 WB W B Loose Pack - Horizontal 95 Duplicate 1 116 CT W B Loose Pack - Horizontal 96 1 117 CT W B Loose Pack - Horizontal 97 1 118 CT W B Loose Pack - Horizontal 98 1 119 CT W B Loose Pack - Horizontal 99 1 120 CT W B Loose Pack - Horizontal 100 1 121 CP D B Loose Pack - Horizontal 165 1 122 CP D B Loose Pack - Horizontal 166 1 123 CP D B Loose Pack - Horizontal 167 1 124 CP D B Loose Pack - Horizontal 168 1 125 N/A N/A N/A Control Inside Autoclave 217 Run 1 Full Exposur

Control 

3-3
Table 3-1 (Continued) 

3-4 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

2 201 WB D B Dense Pack 1 2 202 WB D T Dense Pack 2 2 203 WB D M Dense Pack 3 2 204 WB D M Dense Pack 4 2 204 WB D M Dense Pack 13 Duplicate 2 205 WB D M Dense Pack 5 2 206 WB D M Dense Pack 6 2 207 WB D T Dense Pack 7 2 208 WB D T Dense Pack 8 2 209 WB D T Dense Pack 9 2 210 WB D B Dense Pack 10 2 211 WB D B Dense Pack 11 2 212 WB D B Dense Pack 12 2 213 WB W T Dense Pack 66 2 214 WB W M Dense Pack 67 2 215 WB W B Dense Pack 68 2 216 WB W B Dense Pack 69 2 217 WB W B Dense Pack 72 Duplicate 2 217 WB W B Dense Pack 70 2 218 WB W B Dense Pack 71 2 219 WB W T Dense Pack 73 2 220 WB W T Dense Pack 74 2 221 WB W T Dense Pack 75 2 222 WB W M Dense Pack 76 2 223 WB W M Dense Pack 77 2 224 WB W M Dense Pack 78 2 225 N/A N/A N/A Control Inside Autoclave 218 Run 2 Full Exposur

Control 
Table 3-1 (Continued) 

3-5 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

4 401 CP W N/A N/A 136 4 402 CP W N/A N/A 137 4 403 CP W N/A N/A 138 4 404 CP W N/A N/A 139 4 405 CP W N/A N/A 140 4 406 CP W N/A N/A 141 4 407 CP W N/A N/A 142 4 408 CP W N/A N/A 143 4 409 CP D B Loose Pack - Horizontal 169 4 410 CP D B Loose Pack - Horizontal 170 4 411 CP D B Loose Pack - Horizontal 171 4 411 CP D B Loose Pack - Horizontal 172 Duplicate 4 412 CP D B Loose Pack - Horizontal 173 4 413 CP D M Dense Pack 174 4 414 CP D B Dense Pack 175 4 415 CP D B Dense Pack 176 4 416 CP D B Dense Pack 177 4 417 CP W B Loose Pack - Horizontal 187 4 418 CP W B Loose Pack - Horizontal 188 4 419 CP W B Loose Pack - Horizontal 189 4 420 CP W B Loose Pack - Horizontal 190 4 420 CP W B Loose Pack - Horizontal 191 Duplicate 4 421 CP W M Dense Pack 192 4 422 CP W T Dense Pack 193 4 423 CP W T Dense Pack 194 4 424 CP W T Dense Pack 195 4 425 N/A N/A N/A Control Inside Autoclave 219 Run 4 Full Exposur

Control 
Table 3-1 (Continued) 

3-6 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

8 801 WB D B Loose Pack - Horizontal 101 8 802 WB D B Loose Pack - Horizontal 102 8 803 WB D B Loose Pack - Horizontal 103 8 804 WB D B Loose Pack - Horizontal 104 8 805 WB D B Loose Pack - Horizontal 105 8 806 CT D B Loose Pack - Horizontal 106 8 807 CT D B Loose Pack - Horizontal 107 8 808 CT D B Loose Pack - Horizontal 108 8 809 CT D B Loose Pack - Horizontal 109 8 810 CT D B Loose Pack - Horizontal 110 8 810 CT D B Loose Pack - Horizontal 111 Duplicate 8 811 WB W B Loose Pack - Horizontal 112 8 812 WB W B Loose Pack - Horizontal 114 8 812 WB W B Loose Pack - Horizontal 113 Duplicate 8 813 WB W B Loose Pack - Horizontal 115 8 814 WB W B Loose Pack - Horizontal 116 8 815 WB W B Loose Pack - Horizontal 117 8 816 CT W B Loose Pack - Horizontal 118 8 817 CT W B Loose Pack - Horizontal 119 8 818 CT W B Loose Pack - Horizontal 120 8 819 CT W B Loose Pack - Horizontal 121 8 820 CT W B Loose Pack - Horizontal 122 8 821 Couch D N/A N/A 213 8 822 Couch D N/A N/A 214 8 823 Couch D N/A N/A 215 8 824 Couch D N/A N/A 216 8 825 N/A N/A N/A Control Inside Autoclave 220 Run 8 Full Exposur

Control 
Table 3-1 (Continued) 

3-7 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

5 501 WB W N/A Vertical - Uncut 159 5 502 WB W N/A Vertical - Uncut 160 5 503 WB W N/A Vertical - Uncut 161 5 504 CT W N/A Vertical - Cut 43 5 505 CT W N/A Vertical - Cut 44 5 505 CT W N/A Vertical - Cut 45 Duplicate 5 506 CT W N/A Vertical - Cut 46 5 507 WB D N/A Vertical - Uncut 130 5 508 WB D N/A Vertical - Uncut 131 5 509 WB D N/A Vertical - Uncut 132 5 510 CT W N/A Vertical - Uncut 50 5 511 CT W N/A Vertical - Uncut 51 5 512 CT W N/A Vertical - Uncut 52 5 513 CP W N/A Vertical - Uncut 202 5 514 CP W N/A Vertical - Uncut 203 5 515 CP W N/A Vertical - Uncut 204 5 516 CP D N/A Vertical - Uncut 179 5 517 CP D N/A Vertical - Uncut 180 5 518 CP D N/A Vertical - Uncut 181 5 518 CP D N/A Vertical - Uncut 182 Duplicate 5 519 CT D N/A Vertical - Cut 60 5 520 CT D N/A Vertical - Cut 61 5 521 CT D N/A Vertical - Cut 62 5 522 CT D N/A Vertical - Uncut 63 5 523 CT D N/A Vertical - Uncut 64 5 524 CT D N/A Vertical - Uncut 65 5 525 N/A N/A N/A Control Inside Autoclave 221 Run 5 Full Exposur

Control 
Table 3-1 (Continued) 

3-8 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

6 601 WB W N/A Vertical - Cut 147 6 602 WB W N/A Vertical - Cut 148 6 602 WB W N/A Vertical - Cut 149 Duplicate 6 603 WB W N/A Vertical - Cut 150 6 604 CT D N/A Vertical - Cut 17 6 605 CT D N/A Vertical - Cut 18 6 606 CT D N/A Vertical - Cut 19 6 607 WB D N/A Vertical - Cut 133 6 608 WB D N/A Vertical - Cut 134 6 609 WB D N/A Vertical - Cut 135 6 610 CT D N/A Vertical - Cut 24 6 611 CT D N/A Vertical - Cut 25 6 612 CT D N/A Vertical - Cut 26 6 613 CP W N/A Vertical - Cut 198 6 614 CP W N/A Vertical - Cut 199 6 615 CP W N/A Vertical - Cut 200 6 616 CT W N/A Vertical - Cut 30 6 616 CT W N/A Vertical - Cut 31 Duplicate 6 617 CT W N/A Vertical - Cut 32 6 618 CT W N/A Vertical - Cut 33 6 619 CP D N/A Vertical - Cut 184 6 620 CP D N/A Vertical - Cut 185 6 621 CP D N/A Vertical - Cut 186 6 623 N/A N/A N/A Control Inside Autoclave 222 Run 6 Full Exposur

Control 

6 624 CT W N/A Vertical - Cut 37 6 625 CT W N/A Vertical - Cut 38 6 626 CT W N/A Vertical - Cut 39 
Table 3-1 (Continued) 

3-9 

Run 

Number

Thermocouple 

Number

Material Type 

(WB = Wallboard, 

CT = Ceiling Tiles, 

CP = Carpet)

Moisture 

Content 

(W = Wet, 

D = Dry)

Depth in 

Bin

Packing Density/ Additional 

Notes

BI Test Pouch 

Number

Type of BI Contro

Sample

Control N/A N/A N/A N/A N/A 205 Negative Control - D

Wallboard 

Control N/A N/A N/A N/A N/A 206 Negative Control - W

Wallboard 

Control N/A N/A N/A N/A N/A 207 Negative Control - D

Ceiling Tiles 

Control N/A N/A N/A N/A N/A 208 Negative Control - W

Ceiling Tiles 

Control N/A N/A N/A N/A N/A 209 Negative Control - D

Carpet 

Control N/A N/A N/A N/A N/A 210 Negative Control - W

Carpet 

Control N/A N/A N/A N/A N/A 211 Negative Control - D

Empty Bag 

Control N/A N/A N/A N/A N/A 212 Negative Control - W

Empty Bag 

Control N/A N/A N/A N/A N/A 223 Negative Control - D

Empty Bag 

N/A – Not applicable. 
 3-10

3.3.2.2 Temperature 

 All thermocouples were checked for quality using the procedure outlined in 

Section 6.3 of the QAPP prior to the test. All thermocouples met the acceptance criteria and 

were accurate to within ± 0.7°F compared to a known reference thermometer. Reference testing 

was conducted at 275°F. 

 Thermocouples placed into each load were connected to a data logger through a 

27-channel interface device. The thermocouple at each sample location was uniquely numbered 

using a system where the last two digits ran in a sequence from 01 to 24. Channels 25, 26, and 

27 were used as spares or controls. Numbered thermocouples were connected in the same 

sequence to corresponding data logging channels. For example, thermocouple 101 was 

connected to channel 01, 102 to 02, and so forth. The instrumentation technician made the 

connections, which were verified by the ERG test director. 

 One thermocouple channel was used to monitor ambient conditions outside the 

autoclave to verify the data acquisition system was functioning properly. This temperature 

stayed relatively constant throughout each run, varying between 60 and 75°F. A thermocouple 

also was mounted near the top of one of the autoclave bins in each run, fully exposed to 

autoclave conditions. These data tracked closely with the process temperature measurements for 

all runs except Run 2. The thermocouple reading for the fully exposed autoclave temperature in 

Run 2 (thermocouple 225) suddenly dropped approximately 20°F, 18 minutes into cycle. After 

the autoclave cycle was complete, the thermocouple and corresponding BI test pouch were found 

to have fallen from their mount on the autoclave bin wall into the bulk of BDR mass being 

tested. For all subsequent runs, the thermocouple was mounted using a c-clamp rather than duct 

tape, and a second control thermocouple was placed near the bottom of the bin so that fully 

exposed thermocouples were placed near the top and toward the bottom of an autoclave bin. 

Note that a fully exposed control BI test pouch was only placed next to the top control 

thermocouple. Fully exposed control thermocouple readings were consistent with process 

temperature readings on all subsequent runs. 
 3-11

 During the runs, thermocouples 102, 401, and 423 failed and either stopped 

providing a signal or sent negative temperature readings. Significant signal noise was also 

observed in thermocouples 108, 117, 118, 121, and 814. During Run 1, condensate from steam 

that traveled inside the sheathed thermocouple wire collected on the thermocouple connectors 

outside the autoclave. The condensate collecting within the connectors likely caused the signal 

noise and in some cases failure of the thermocouples in Run 1. After Run 1, the connectors were 

inverted to force the condensate to drip off the wires instead of collecting in the connectors, 

which eliminated most of the signal noise and failure problems. Of the 162 time/temperature 

data series, 156 were collected satisfactorily, resulting in 96 percent complete data. Therefore, 

the acceptance criteria of at least 80 percent of the data being collected satisfactorily was met. 

 No data from the three thermocouples that failed were used for the analyses in this 

report. Data from the five thermocouples with significant noise were used. Most of the noise 

resulted in abrupt temperature spikes or dips of less than 50°F. However, there were two data 

spikes for thermocouple 118 where the temperature reading more than doubled for 

approximately 20 seconds. This is characteristic of no signal being received by the data logger 

for a short period. Data from the data point immediately preceding the spikes were extrapolated 

and used for data analyses instead of the temperature spike data for these two instances for 

thermocouple 118. All other temperature data were used as recorded. 

3.3.2.3 Test Conditions 

 The ERG test engineer recorded the test conditions on log sheets as identified in 

the QAPP. The ERG test engineer and ERG test director verified and signed all log sheets for 

each run. 

3.3.2.4 BI Test Strip Results 

 Raven Biological Laboratories, Inc. analyzed the BI test strips. All samples were 

successfully analyzed, providing a100 percent complete data set. 
 3-12

 Three sets of control BI pouches were analyzed. First, two duplicate sample 

pouches were placed within each test run, adjacent to the sample pouch it was duplicating. Of 

the 12 duplicate pouches, 10 yielded the same results as the corresponding sample pouches (i.e., 

growth was found in both in one case and no growth was found in both in nine cases). However, 

at two of the sample points (thermocouples 217 and 812) the growth/no-growth results for the 

duplicates did not match (i.e., the ‘A’ strip for the duplicate indicated growth and the ‘A’ strip 

for the sample did not). The ‘B’ strips for the duplicates were assayed and no viable survivor 

population was found (<100 CFU), consistent with the A strip of the original sample. These data 

suggest that, in some cases, a growth indication alone may be a false positive result (2 of the 12 

cases measured). However, the growth/no-growth indication coupled with the BI assay data is a 

reliable measure of sterilization and spore viability. 

 Additionally, nine blind control samples were analyzed that were not exposed to 

autoclave conditions, but in all other respects handled the same as other BI test pouches. These 

nine controls all yielded positive results for growth, and the assay data confirm that no 

significant reduction in viable spores was caused by the handling, packaging, and shipping of the 

BI pouches. 

 Finally, one blind control test pouch was autoclaved in each run, not embedded in 

any building material and exposed fully to autoclave conditions. These controls for all runs 

except Run 2 yielded negative results for growth. Upon analyzing the assay data for the Run 2 

control, only a 104

 reduction in viable spores was achieved. As mentioned previously, the 

thermocouple and corresponding BI test pouch for Run 2 fell from their mount on the autoclave 

bin wall and became embedded in the BDR mass in Run 2. This caused the BI test pouch not to 

be fully exposed to the autoclave conditions and is likely the cause of the remaining spore 

viability. No growth was observed in every other quality assurance sample fully exposed 

throughout the test. 
Figure 3-1. Run 1 Time/Temperature Data

507090

110130150170190210230250270290310330350

0 20 40 60 80 100 

Time (min)

Temperature (°F)

Run 1 - 31.5psig/275°Multiple BDR Types Loose Pack 

DWB - Dry Wallboard; WWB - Wet Wallboard; DCT - Dry Ceiling Tiles; WCT - Wet Ceiling Tiles; DCP - Dry Carpet; CON - Fully 

Exposed Control; REF - Exterior Reference Temperature

 3-13
Figure 3-2. Run 2 Time/Temperature Data

507090

110130150170190210230250270290310

0 20 40 60 80 100 120 

Time (min)

Temperature (°F)

DWB - Dry Wallboard; WWB - Wet Wallboard; T - Top of Dense Pack Bin; M - Middle of Dense Pack Bin; B - Bottom of Dense Pack 

CON - Fully Exposed Control; REF - Exterior Reference Temperature

Run 2 - 45psig/292°FWallboard - Dense Pack 

3-14
Figure 3-3. Run 4 Time/Temperature Data

507090

110130150170190210230250270290310

0 20 40 60 80 100 120 140

Time (min)

Temperature (°F)

DCP - Dry Carpet; WCP - Wet Carpet; Roll - Large Carpet Roll; T - Top of Dense Pack Bin; M - Middle of Dense Pack Bin; B - Botto

Dense Pack Bin CON - Fully Exposed Control; REF - Exterior Reference Temperature

Run 4 - 31.5psig/275°FCarpet - Loose, Dense, and Large Roll

3-
Figure 3-4. Run 8 Time/Temperature Data

507090

110130150170190210230250270290310

0 20 40 60 80

Time (min)

Temperature (°F)

DWB - Dry Wallboard; WWB - Wet Wallboard; DCT - Dry Ceiling Tiles; WCT - Wet Ceiling Tiles; CON - Fully Exposed Control; R

Exterior Reference Temperature

Run 8 - 45psig/292°FMultiple BDR Types Loose Pack 

3-16
Figure 3-5. Run 5 Time/Temperature Data

507090

110130150170190210230250270290310

0 10 20 30 40 50 60 70 80 90 

Time (min)

Temperature (°F)

DWB - Dry Wallboard; WWB - Wet Wallboard; DCT - Dry Ceiling Tiles; WCT - Wet Ceiling Tiles; DCP - Dry Carpet; 

WCP - Wet Carpet; CON - Fully Exposed Control; REF - Exterior Reference Temperature

Run 5 - 31.5psig/275°FMultiple BDR Types Vertical - Two Cycles

3-17
Figure 3-6. Run 6 Time/Temperature Data

507090

110130150170190210230250270290310

0 10 20 30 40 50 60 70 

Time (min)

Temperature (°F)

DWB - Dry Wallboard; WWB - Wet Wallboard; DCT - Dry Ceiling Tiles; WCT - Wet Ceiling Tiles; DCP - Dry Carpet; 

WCP - Wet Carpet; CON - Fully Exposed Control; REF - Exterior Reference Temperature

Run 6 - 31.5psig/275°FMultiple BDR Types - Vertical - Two Cycles - All Bags Cut

3-18
 4-1

4.0 DISCUSSION

 As discussed previously, the following variables were identified as having a 

potential impact on sterilization capability: 

1. Item type; 

2. Autoclave packing density (i.e., loose packing versus dense packing); 

3. Moisture content of autoclaved materials; 

4. Autoclave temperature/pressure; and 

5. Time in autoclave. 

 During the test, three additional factors were identified as potentially influencing 

sterilization capability: 

1. Positioning sample bags of BDR vertically instead of horizontally; 

2. Cutting open the bags of BDR to facilitate steam penetration; and 

3. Running two shorter process cycles in sequence instead of one long cycle. 

 One additional factor that may affect sterilization not investigated in this study 

was the packaging technique. BDR was cut up, double bagged in 1.8 mil autoclave bags, and 

goose-necked closed with duct tape, to mimic BDR generated from a likely disposal incident. 

Other packaging techniques (e.g., bag/container type, bag thickness, quantity of BDR per bag, 

and sealing method) that may also influence sterilization ability were not evaluated. 

 This section first discusses the impact of the observed time/temperature profiles 

on BDR sterilization, measured using the BI growth/no-growth and assay results. The section 

then presents how each of the variables above affected the temperature profile and associated 

sterilization results. 

4.1 Time and Temperature Effect on Sterilization

Figures 4-1 through 4-3 present the time and temperature affect on sterilization 

for Runs 2, 4, and 5. All figures are located at the end of this section. On each figure, the 

time/temperature profile is plotted, and the lines are color coded to indicate whether the 
 4-2

associated BI data indicated viable spores or no viable spores. A viable spore designation is used 

if growth was found in both the growth/no-growth test and the assay analysis. Sterilization or a 

no viable spore designation is used if no growth was found in the growth/no-growth test with an 

106 initial BI population. In a limited number of cases, the growth/no-growth test indicated a 

positive result; however, no quantifiable population was measured by the subsequent assay 

analysis (reported result of <100 CFU). These data series are labeled as indeterminate. 

 No figures are provided for Runs 1, 8, and 6 because no viable spores were found 

in these runs. The temperature profiles for these runs can be viewed on Figures 3-1, 3-4, and 3-6, 

respectively. Each of these runs contained loose pack BDR materials, processed at different 

conditions. 

 The spores were sterilized in all cases where the target of 15 minutes at 250°F 

was achieved. While spores were also sterilized in several instances below this target, 15 

minutes at 250°F was required to ensure sterilization. The effect of each variable on sterilization 

is discussed in the following subsections. 

4.2 Item Type and Moisture Content

 The temperature profiles for Runs 1, 8, 5, and 6, presented in Figures 4-4 through 

4-7, respectively, show the influence of item type on temperature profile. Within each of these 

runs, different item types were autoclaved under the same conditions. An average data series is 

provided for each item type on each figure. The average data series were calculated as the 

arithmetic average of the temperature at each time T, at every sampling location of that type. For 

example, in Run 1, there were five wet ceiling tile sampling locations. The temperature plotted 

for the wet ceiling tile series at T = 20 minutes is the average of the temperatures at each of the 

five wet ceiling tile locations at T = 20 minutes. Where averages were calculated, the number of 

sample points averaged is presented next to each series. 

 As shown on the figures, dry carpet and dry ceiling tiles heated more rapidly than 

wet carpet and wet ceiling tiles, respectively. Dry wallboard and wet wallboard heated at 

approximately the same rate in three of the four runs where comparison can be made (Figures 4-
 4-3

4, 4-5, 4-7). In Run 5 (Figure 4-6), the wet wallboard heated significantly faster. These 

differences are believed to be functions of the moisture content of each material. The difference 

between dry and wet carpet and ceiling tile results are likely due to the significant water 

absorbing-capacity of carpet (53 percent increase in weight when wet) and ceiling tiles (34 

percent increase in weight when wet). The significant water content of the wet carpet and ceiling 

tiles increases the thermal load needed to boil the water and heat the material in the autoclave 

and may also decrease steam penetration. 

 Wallboard does not absorb as much water when wet (9 percent increase in weight 

when wet). This would explain the relatively similar results for wet and dry wallboard observed 

on Figures 4-4, 4-5, and 4-7. 

 With respect to differing item types, wet wallboard heated faster than wet ceiling 

tiles, which heated faster than wet carpet. This relationship was observed in all runs and is 

consistent with the relative water-absorbing capacity of each material, as discussed above. When 

moisture content is eliminated as a variable and dry BDR items are compared to each other, there 

is no apparent trend. For example, dry carpet heated fastest in Run 1, but slower than dry ceiling 

tiles and dry wallboard in Run 6. Similarly, dry ceiling tiles heated fastest in Run 6, but slower 

than dry wallboard and dry carpet in Run 5. These observations suggest that trends and 

differences in heating rates between BDR item types depends primarily on the moisture content 

of wet items, and not on the BDR material itself. 

 The sofa, tested dry, heated more rapidly than wallboard and ceiling tiles in the 

one run where it was tested (Figure 4-5). If it had been saturated with water, the results may 

have been significantly different, based on the findings for ceiling tiles and carpet. 

4.3 Autoclave Packing Density and Location

 The effect of autoclave packing density is best isolated from other variables by 

examining the data for Runs 2, 4, and 8. Wet and dry wallboard were tested in both loose pack 

(one layer of bags) and dense pack arrangement (approximately four layers of bags) in Runs 2 

and 8, respectively. Both runs were conducted at 45 psig (292°F). Figure 4-8 presents average 
 4-4

time/temperature profile data for each set of conditions. Carpet was tested in both a loose pack 

and dense pack arrangement in Run 4 at 31.5 psig (275°F); Figure 4-9 presents average 

time/temperature profile data. As shown by these figures, loose pack items heat significantly 

faster than dense pack. Most of the dense pack sample points never achieved the target 

temperature of 250°F for 15 minutes, and resulted in significant remaining spore viability (see 

Figures 4-1 and 4-2). The majority of the positive growth results found during the test were in 

the dense packing configuration. 

 The temperature profile within the thermal mass was investigated using data from 

Run 2. Figure 4-10 presents average data from dense pack wallboard in Run 2 at varying levels 

within the mass. Top layer data points are from thermocouples in bags at the top of the mass, 

exposed to the autoclave conditions; middle layer data points are from bags in between other 

bags; and bottom layer data point are from bags touching the bottom of the bin. As shown by 

these data, the bags at the bottom of the bin heated fastest, indicating conduction through the 

metal bin may be a factor in heating the BDR. However, remaining viable spores were found in 

all three layers of densely packed material. 

 Selected wallboard bags were examined to investigate the temperature profile 

within the 3-sample bags. Figure 4-11 presents two examples, comparing the temperature profile 

within a dry loose pack wallboard bag and a dry dense pack, middle layer wallboard bag. As 

shown in the loose pack bag, while the center of the bag generally heated more slowly, all three 

temperature readings gradually converge, and the spores were all sterilized at all three locations. 

However, there was not enough time for the bag in the dense pack configuration to reach a 

sterilization temperature. Sterilization was only achieved between the first and second sheet. 

 Figure 4-12 presents the temperature profile within selected loose pack ceiling tile 

bags. Similarly, the center of the bags heated slowest. However, all sample points came up to 

temperature and all spores were sterilized in the loose pack arrangement. 
 4-5

4.4 Temperature and Pressure

 As mentioned previously, autoclave temperature and pressure are related 

variables, as the autoclave is designed to operate at saturated steam conditions. Two conditions 

were investigated: 31.5 psig/275°F, the typical operating pressure of the autoclave, and 45 

psig/292°F, the maximum operating pressure of the autoclave. The effect of autoclave 

temperature and pressure is best isolated from other variables by examining the data from Runs 1 

and 8. Loose pack, wet and dry wallboard and ceiling tiles were processed in Run 1 at 31.5 

psig/275°F and in Run 8 at 45 psig/292°F. Figure 4-13 compares the wallboard data collected 

for Run 1 versus Run 8, and Figure 4-14 compares the ceiling tile data for both runs. For both 

materials, the higher temperature and pressure accelerated the BDR heating process significantly. 

However, all BIs from both runs exhibited no growth. Run 1 at the lower temperature was 

conducted for 120 minutes while Run 8 at the higher temperature was terminated after 75 

minutes. 

4.5 Packing Orientation

 Materials were tested both lying horizontally and positioned vertically. The 

vertical packing arrangement was only tested in loose packing configuration using two 40-

minute autoclave cycles in sequence. The packing orientation variable is best isolated by 

comparing wallboard and ceiling tile data between Runs 1 and 5 and carpet data between Runs 4 

and 5. Figures 4-15 through 4-17, respectively, present the average data for these runs for each 

item type. In reviewing these figures, only data for the first 40 minutes should be considered for 

comparison purposes, as that is when the postvacuum cycle began during Run 5, which is 

different from Runs 1 and 4. Accounting for the different starting temperatures between the 

runs, the data appear variable and no firm conclusions can be drawn about the influence of 

packing orientation on autoclave performance. 
 4-6

4.6 Open Bags

 Runs 5 and 6 were performed under the same conditions, except that two of the 

eight bags tested were sliced open prior to autoclaving in Run 5 and all of the bags were sliced 

open prior to autoclaving in Run 6. Figures 4-18, 4-19, and 4-20 present the average data from 

these runs, comparing results for cut and uncut bags for wallboard, ceiling tiles, and carpet, 

respectively. The data available to make this comparison are limited and somewhat variable. In 

most cases, the data presented are for three sample locations within one bag of BDR. As seen on 

Figure 4-18, wet wallboard in an uncut bag heated most rapidly. On Figure 4-19, ceiling tiles in 

cut bags heated most rapidly. On Figure 4-20, dry carpet in an uncut bag heated most rapidly, 

but wet carpet in an uncut bag heated most slowly. This uncut bag of wet carpet was the only 

bag in Runs 5 or 6 to contain biological indicators with surviving spores. All other biological 

indicators from these runs exhibited no surviving spores. 

 It is worth noting that even bags that were not cut open prior to autoclaving had a 

tendency to rupture in the autoclave when subjected to the pressure differentials and heat of the 

autoclave cycle. 

 Based on these data, we cannot draw any firm conclusions regarding the impact of 

cutting bags open prior to autoclaving. 

4.7 Two Sequential Cycles

 As illustrated in Figures 3-5 and 3-6, conducting two standard autoclave cycles in 

sequence proved to be quite effective in bringing BDR items up to the full autoclave temperature 

rapidly after steam is applied during the second cycle. We believe that applying a vacuum 

between the first and second cycles is what is particularly effective about this approach. The 

first cycle acts to preheat the material, although it is likely that the initial contact between the 

steam and the BDR material results in immediate condensation, filling pore spaces within the 

material. Consequently, steam supplied later in the cycle does not penetrate well into the 

material, and the material only slowly heats due to free convection and conduction from the bin 

walls. Applying a vacuum prior to the second cycle likely pulls the condensate away from the 
 4-7

material, and when steam is subsequently applied, it penetrates well into the material, which 

quickly rises to the full autoclave temperature. In fact, Run 6 was terminated early because all 

BDR materials had been over 270°F for 15 minutes well before the second cycle was scheduled 

to be completed. When subjected to two autoclave cycles in sequence, all biological indicators 

except for those in the one bag of wet carpet in Run 5 exhibited no surviving spores. Two 

autoclave cycles did not consistently result in no-growth for BI test strips placed in wet carpet. It 

may be necessary to further process wet carpet beyond two cycles to effectively sterilize it. 
Figure 4-1. Run 2 Spore Viability

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0 20 40 60 80 100 

Time (min)

Temperature (°F)

No Viable Spores Viable Spores Spore Viability Indeterminate

Run 2 Wallb45psi

4-8
Figure 4-2. Run 4 Spore Viability

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0 20 40 60 80 100 

Time (min)

Temperature (°F)

No Viable Spores Viable Spores Spore Viability Indeterminate

RCD3

4-9
Figure 4-3. Run 5 Spore Viability

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0 10 20 30 40 50 60 70 80 

Time (min)

Temperature (°F)

No Viable Spores Viable Spores

Run 5 Multiple BDR Vertical - Tw31.5psig/275

4-10
Figure 4-4. Run 1 Moisture Content and Item Type Comparison

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0 20 40 60 80 

Time (min)

Temperature (°F)

Dry Ceiling Tiles (5 points)

Wet Ceiling Tiles (5 points)

Dry Wallboar

Wet Wallboard (5 points)

Dry Carpet (4 points)

RuMLo31

Each line on this 

gra

ph is an avera

ge of multi

ple sam

ple 

points. The number of sam

ple 

points avera

ged is 

presented ne

4-11
Figure 4-5. Run 8 Moisture Content and Item Type Comparison

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Time (min)

Temperature (°F)

Run MuLoo45p

Wet Ceiling Tiles (5 points)

Dry Ceiling Tiles (5 points)

Dry Wallboard (5 points)

Wet Wallboard (5 points)

Sofa (4 points)

Each line on this 

gra

ph is an avera

ge of multi

ple sam

ple 

points. The number of sam

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points avera

ged is 

presented nex

4-12
Figure 4-6. Run 5 Moisture Content and Item Type Comparison (Uncut Bags O

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Time (min)

Temperature (°F)

Run 5 MultipVertic31.5p

Wet Wallboard (3 points)Dry Wallboard (3 points)

Dry Carpet (3 points)

Wet Ceiling Tiles (3 points)

Dry Ceiling Tiles (3 points)

Wet Carpet (3 points)

Each line on this 

gra

ph is an avera

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ple sam

ple 

points. The number of sam

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points avera

ged is 

presented ne

4-13
Figure 4-7. Run 6 Moisture Content and Item Type Comparison

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Time (min)

Temperature (°F)

RMVA3

Wet Carpet (3 points)

Dry Carpet (3 points)

Wet Ceiling Tiles (6 points)

Dry Ceiling Tiles (6 points)

Dry Wallboard (3 points)

Wet Wallboard (3 points)

Each line on this 

gra

ph is an avera

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points. The number of sam

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points avera

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presented ne

4-14
Figure 4-8. Wallboard Packing Density Comparison

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Time (min)

Temperature (°F)

Run 8 Dry Wallboard Loose Pack (5 points)

Run 8 Wet Wallboard Loose Pack (5 points)

Run 2 Dry Wallboard Dense Pack (12 points)

Run 2 Wet Wallboard Dense Pack (12 points)

Each line on this 

gra

ph is an avera

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ple sam

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points. The number of sam

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points avera

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presented ne

4-15
Figure 4-9. Carpet Packing Density Comparison

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Time (min)

Temperature (°F)

Run Carpeand L31.5p

Dry Carpet Dense Pack (4 points)

LargeWet Carpet Roll (7 points)

Wet Carpet Dense Pack (3 points)

Wet Carpet Loose Pack (4 points)

Dry Carpet Loose Pack (4 points)

Each line on this graph is an average of multiple sample points. The number of sample points averaged is presented ne

4-16
Figure 4-10. Run 2 Dense Packing Layer Comparison

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Time (min)

Temperature (°F)

RWD4

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points. The number of sam

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points avera

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presented ne

Dry Wallboard Middle Layer (4 points)

Dry Wallboard Bottom Layer (4 points)

Wet Wallboard Bottom Layer (4 points)

Wet Wallboard Top Layer (4 points)

Wet Wallboard Mid

Dry Wallboard Top Layer (4 

4-17
Figure 4-11. Comparison of Sample Points Within Selected Wallboard Ba

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Time (min)

Temperature (°F)

RML3RWD4

Run 1 Dry Wallboard Loose Pack

Between 1st and 2nd sheet

Between 2nd and 3rd sheet

Between 4th and 5th sheet

Run 2 Dry Wallboard Dense Pack - Middle Layer

Between 4th and 5th sheet

Between 2nd and 3rd sheet

Between 1st and 2nd sheet

Note: 1st sheet was alwa

ys on to

p in the bins.

4-18
Figure 4-12. Comparison of Sample Points within Selected Ceiling Tile Ba

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Time (min)

Temperature (°F)

RuMLo31RuMVe31

Note: 1st sheet was alwa

ys on to

p in the bins.

Run 5 Dry Vertical Ceiling Tiles

Between 2nd and 3rd sheet

Between 4th and 5th sheet

Between 7th and 8th sheet

Run 1 Dry Horizontal Ceiling Tiles

Between 2nd and 3rd sheet

Between 4th and 5th sheet

Between 7th and 8th sheet

4-19
Figure 4-13. Autoclave Temperature Comparison for Wallboard

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Time (min)

Temperature (°F)

Each line on this 

gra

ph is an avera

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points. The number of sam

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points avera

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presented ne

RML4

RMLo31

Run 8 - 292°F Wet Wallboard (5 points)

Run 8 - 292°F Dry Wallboard (5 points)

Run 1 - 275°F Wet Wallboard (5 points)

Run 1 - 275°F Dry Wallboard (4 points)

4-20
Figure 4-14. Autoclave Temperature Comparison for Ceiling Tiles

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Time (min)

Temperature (°F)

Run 1 - 275°F Dry Ceiling Tiles (5 points)

Run 8 - 292°F Dry Ceiling Tiles (5 points)

Run 8 - 292°F Wet Ceiling T

Run 1 - 275°F Wet Ceiling Tiles (5 points) R

ML4RML3

Each line on this 

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points avera

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presented ne

4-21
Figure 4-15. Horizontal Versus Vertical Packing Orientation for Wallboard

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Time (min)

Temperature (°F)

RuMuLo31RuMuVe31

Each line on this 

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points. The number of sam

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points avera

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presented nex

Run 1 Wet Horizontal W

Run 1 Dry Horizontal Wallboard (4 

Run 5 Dry Vertical Wallboard (3 points)

Run 5 Wet Vertical Wallboard (3 points)

4-22
Figure 4-16. Horizontal Versus Vertical Packing Orientation for Ceiling Tiles

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Time (min)

Temperature (°F) Run 1 Dry Horizontal Ceiling 

Run 5 Wet Vertical Ceiling Tiles - Uncut Bags Only (3 points)

Run 5 Dry Vertical Ceiling Tiles - Uncut Bags Only (3 points)

Run MuLoo31.5Run MuVer31.5

Each line on this 

gra

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points. The number of sam

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points avera

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presented ne

Run 1 Wet Horizontal Ceiling Tiles (5 points)

4-23
Figure 4-17. Horizontal Versus Vertical Packing Orientation for Carpet

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Time (min)

Temperature (°F)

Run MulVer31.5Run Carand 31.5

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points. The number of sam

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points avera

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presented ne

Run 4 Wet Horizontal Carpet 

Run 4 Dry Horizontal Carpet (4 points)

Run 5 Wet Vertical Carpet (3 points)

Run 5 Dry Vertical Carpet (3 points)

4-24
Figure 4-18. Cut Versus Uncut Wallboard Bags

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Time (min)

Temperature (°F)

Each line on this graph is an average of multiple sample points. The number of sample points averaged is presented ne

RuMuVerWa31.RuMuVerAll 31.

Run 5 Wet Wallboard Uncut (3 points)

Run 6 Dry Wallboard Cut (3 points)

Run 5 Dry Wallboard Uncut (3 points)

Run 6 Wet Wallboard Cut (3 points)

4-25
Figure 4-19. Cut Versus Uncut Ceiling Tile Bags

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Time (min)

Temperature (°F)

Run 5 MultipVerticCut a31.5p

Each line on this graph is an average of multiple sample points. The number of sample points averaged is presented ne

Run 5 Wet Ceiling Tiles Uncut (3 points)

Run 5 Dry Ceiling Tiles Uncut (3 points)

Run 5 Dry Ceiling Tiles Cut (3 points)

Run 5 Wet Ceiling Tiles Cut (3 points)

4-26
Figure 4-20. Cut Versus Uncut Carpet Bags

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Time (min)

Temperature (°F) Ru

MVeCa31RuMVeAl31

Run 5 Dry Carpet Uncut (3 points)

Run 5 Wet Carpet Uncut (3 points)

Run 6 Dry Carpet Cut (3 points)

Run 6 Wet Carpet Cut (3 points)

Each line on this graph is an average of multiple sample points. The number of sample points averaged is presented ne

4-27
 5-1

5.0 CONCLUSIONS

 Based on variables evaluated in this study, the following conclusions can be 

drawn regarding processing of BDR material in a commercial-scale autoclave. Conclusions 

regarding sterilization are based on a finding of no growth, using 106

 population BI test strips. 

General Conclusions

C Achieving an internal BDR material temperature of 250°F or higher for 15 

minutes or longer destroyed all biological indicators. The following approaches 

were most effective in achieving this: using a loose packing configuration, 

processing dry BDR material, establishing higher autoclave operating temperature 

and pressure, and running multiple autoclave cycles in sequence. 

 

C Bagged wallboard (wet or dry), ceiling tiles (wet or dry), and dry carpet can be 

effectively sterilized under appropriate time, temperature, and packing conditions. 

Time, temperature, and packing requirements are provided below. 

C Dry upholstered furniture can be effectively sterilized. No conclusions are drawn 

regarding wet upholstered furniture. 

Time, Temperature, and Pressure Effects

C An autoclave cycle of 120 minutes at 31.5 psig/ 275°F effectively sterilized 

wallboard, ceiling tiles, and dry carpet, when loaded in the autoclave as described 

below. 

C An autoclave cycle of 75 minutes at 45 psig/ 292°F effectively sterilized 

wallboard and ceiling tiles, when loaded in the autoclave as described below. 

C Two standard autoclave cycles of 40 minutes and 31.5 psig/ 275°F run in 

sequence effectively sterilized wallboard, ceiling tiles, and dry carpet, when 

loaded as described below. Available data suggest the second cycle can be 

shortened to 20 minutes. Two autoclave cycles did not consistently result in no 

growth for BI test strips placed in wet carpet. It may be necessary to further 

process wet carpet beyond two cycles for effective sterilization. It appears that 

evacuating the autoclave between the first the second cycle is critical, allowing 

the second cycle to successfully sterilize the BDR. 

Autoclave Loading

C Bags of BDR material should be placed in the autoclave so that all surfaces are 

exposed to autoclave conditions. Bags lying flat against a metal surface, such as 

the base of an autoclave bin, are considered to be fully exposed to autoclave 

conditions. 
 5-2

C Bags of BDR material stacked or nested such that they are not fully exposed to 

autoclave conditions may not be reliably sterilized under the conditions tested. 

C Bags of 1⁄2 inch wallboard slabs up to 5 layers thick and 5/8 inch ceiling tiles up to 

9 layers thick can be effectively sterilized under the time, temperature, and 

packing density conditions described above. 

C Dry commercial grade carpet rolls formed from pieces 26 inches wide and 20 feet 

long can effectively sterilized under the time, temperature, and packing density 

conditions described above. 

 
 6-1

6.0 REFERENCES

1. Quality Assurance Project Plan, Destruction of Spores on Building 

Decontamination Residue in a Commercial Autoclave, prepared by Eastern 

Research Group, Inc., Chantilly, VA, February 21, 2005. 

2. “Work Plan, Waste Removal and Facility Cleaning, Department of State SA-32 

Diplomatic Pouch and Mail Facility Sterling, VA.” Submitted by U.S. Army 

Corps of Engineers, Rapid Response Program and SE&I, Rev 3, November 12, 

2002. 

3. Boca, Pretorius, Gochin, Chapoullie, and Apostolides, 2002. “An Overview of 

the Validation Approach for Moist Heat Sterilization, Part I.” Pharmaceutical 

Technology. September, 2002, pg. 62-70. 

4. Barkley, W. and Richardson, J., 1994. Laboratory Safety, pg. 715-734, in 

Gerhardt, P., Murray, R., Wood, W., and Krieg, N. Methods for General and 

Molecular Bacteriology, ASM. Washington, DC. 
Appendix A 

PHOTOGRAPHIC LOG
A-1 

Photo 1. Healthcare Environmental’s Oneonta, 

New York Facility 

Photo 3. Stacks of Size Reduced Wallboard and 

Ceiling Tiles 

Photo 5. Wallboard on Dry Rack 

Photo 2. Wallboard Size Reduction 

Photo 4. Submersing Wallboard Sheets 

Photo 6. Assembled Sample Point 
A-2 

Photo 7. Sample Point (Thermocouple Paired 

with a BI Test Pouch) 

Photo 9. Palletized Bags of Ceiling Tiles 

Photo 11. Carpet Wetting 

Photo 8. Sample Point Between Sheets of 

Drywall 

Photo 10. Bulk Quantity of Used Commercial 

Carpet 

Photo 12. Sample Point within Carpet 
A-3 

Photo 13. Water Draining out of Assembled 

Carpet Roll 

Photo 15. Assembled Large Carpet Rolls 

Photo 17. Empty Autoclave 

Photo 14. Assembled Bags of Small Carpet Rolls 

Photo 16. Sofa Wrapping 

Photo 18. Empty Autoclave Bin 
A-4 

Photo 19. Autoclave Bins on Transfer Cart 

Photo 21. Flange Port 

Photo 23. Connectors Not Inverted Allowing 

Condensate to Collect in the Connectors 

Photo 20. Bins Loaded into Autoclave 

Photo 22. Fabricated Flange Port to Allow 

Thermocouple Wires to Pass Through 

Photo 24. Connectors Inverted to Allow 

Condensate to Drip Off the Wires 
A-5 

Photo 25. Data Acquisition System 

Photo 27. Loose Pack Wallboard Bin 

Photo 29. Dense Pack Wallboard Bin 

Photo 26. Pallets of BDR Material 

Photo 28. Wallboard Bags After Autoclaving 

Photo 30. Loose Pack Ceiling Tile Bin 
A-6 

Photo 31. Loose Pack Carpet Bin 

Photo 33. Dense Pack Carpet Bin 

Photo 35. Vertical Orientation 

Photo 32. Loose Pack Carpet Bin After 

Autoclaving 

Photo 34. Large Carpet Roll on Pallet for 

Autoclaving 

Photo 36. Vertical Packaging Orientation After 

Autoclaving 
A-7 

Photo 37. Full Exposure Control Sample 

Photo 39. Connecting Thermocouple Wires 

Photo 41. Removing BI Test Pouches from BDR 

Photo 38. Stringing Thermocouple Wires Along 

the Top of the Bins 

Photo 40. Removing BI Test Pouches From Sofa 

Photo 42. BI Test Pouches Packed for Shipment 

to Laboratory 
United States

Environmental Protection

Agency

Offi ce of Research and Development

National Homeland Security Research Center

Cincinnati. OH 45268

Offi cial Business

Penalty for Private Use

$300

EPA/600/R-05/081

April 2005

PRESORTED STANDARD

POSTAGE & FEES PAID

EPA

PERMIT NO. G-35