United States

Environmental Protection

Agency

technolog y evaluation report

Biological Inactivation Efficiency by HVAC 

In-Duct Ultraviolet Light Systems

Atlantic Ultraviolet Corporation 

AeroLogic Model AD24-4

Office of Research and Development

National Homeland Security

Research Center
EPA 600/R-06/051

May 2006 

Technology Evaluation Report 

Biological Inactivation Efficiency 

by HVAC In-Duct Ultraviolet Light 

Systems 

Atlantic Ultraviolet Corporation 

AeroLogic Model AD24-4 

By 

Karin Foarde, Deborah Franke, James Hanley, 

Kathleen Owen and Tricia Webber 

RTI International 

3040 Cornwallis Road 

Research Triangle Park, NC 27709 

Eric Koglin 

Task Order Project Officer 

National Homeland Security Research Center 

Office of Research and Development 

U.S. Environmental Protection Agency 

944 East Harmon Ave. 

Las Vegas, NV 89119 
ii 

Notice

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

National Homeland Security Research Center (NHSRC), funded and managed this technology 

evaluation through a Blanket Purchase Agreement (BPA) under General Services Administration 

contract number GS23F0011L-3 with Battelle, with RTI under subcontract to Battelle. This report has 

been peer and administratively reviewed and has been approved for publication as an EPA document. 

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

use of a specific product. 
iii 

Foreword

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the nation’s 

air, water, and land resources. Under a mandate of national environmental laws, the Agency strives to 

formulate and implement actions leading to a compatible balance between human activities and the 

ability of natural systems to support and nurture life. To meet this mandate, the EPA’s Office of 

Research and Development (ORD) provides data and science support that can be used to solve 

environmental problems and to build the scientific knowledge base needed to manage our ecological 

resources wisely, to understand how pollutants affect our health, and to prevent or reduce environmental 

risks. 

 

In September 2002, EPA announced the formation of the National Homeland Security Research Center 

(NHSRC). The NHSRC is part of the Office of Research and Development; it manages, coordinates, and 

supports a variety of research and technical assistance efforts. These efforts are designed to provide 

appropriate, affordable, effective, and validated technologies and methods for addressing risks posed by 

chemical, biological, and radiological terrorist attacks. Research focuses on enhancing our ability to 

detect, contain, and clean up in the event of such attacks. 

NHSRC’s team of world renowned scientists and engineers is dedicated to understanding the terrorist 

threat, communicating the risks, and mitigating the results of attacks. Guided by the roadmap set forth in 

EPA’s Strategic Plan for Homeland Security, NHSRC ensures rapid production and distribution of 

security-related products. 

The NHSRC has created the Technology Testing and Evaluation Program (TTEP) in an effort to provide 

reliable information regarding the performance of homeland security related technologies. TTEP 

provides independent, quality assured performance information that is useful to decision makers in 

purchasing or applying the tested technologies. It provides potential users with unbiased, third-party 

information that can supplement vendor-provided information. Stakeholder involvement ensures that 

user needs and perspectives are incorporated into the test design so that useful performance information 

is produced for each of the tested technologies. The technology categories of interest include detection 

and monitoring, water treatment, air purification, decontamination, and computer modeling tools for use 

by those responsible for protecting buildings, drinking water supplies and infrastructure, and for 

decontaminating structures and the outdoor environment. 

The evaluation reported herein was conducted by RTI International under contract to Battelle as part of 

the TTEP program. Information on NHSRC and TTEP can be found at 

http://www.epa.gov/ordnhsrc/index.htm. 
iv 

Acknowledgments

The authors wish to acknowledge the support of all those who helped plan and conduct the evaluation, 

analyze the data, and prepare this report. We would like to thank Dr. Leslie E. Sparks, USEPA, and Dr. 

W. Gene Tucker, James Madison University, for their reviews of this report. We also acknowledge the 

assistance and participation of our stakeholder group for their input to the test plan. 
v 

Contents 

Notice.................................................................................................................................................... ii 

Foreword .............................................................................................................................................. iii 

Acknowledgments ................................................................................................................................ iv 

Abbreviations/Acronyms ..................................................................................................................... vii 

Executive Summary.............................................................................................................................. ix 

1.0 Introduction .................................................................................................................................... 1 

2.0 Technology Description .................................................................................................................. 3 

3.0 Test Procedures .............................................................................................................................. 5 

3.1 Operation of the Test Duct.................................................................................................. 5 

3.2 Preparation and Generation of Bioaerosol Challenges......................................................... 6 

3.3 Sampling the Bioaerosols ................................................................................................... 7 

3.4 Bioaerosol Control Efficiency Calculation.......................................................................... 7 

 3.5 Average Dose of UV Delivered by the Device.................................................................... 7 

4.0 Quality Assurance/Quality Control.................................................................................................. 9 

4.1 Equipment Calibration......................................................................................................... 9 

4.1.1 Reference Methods.................................................................................................. 9 

4.1.2 Instrument Checks................................................................................................... 9 

4.2 Audits.................................................................................................................................. 9 

4.2.1 Performance Evaluation Audit................................................................................ 9 

4.2.2 Technical Systems Audit........................................................................................ 9 

4.2.3 Data Quality Audit ................................................................................................10 

4.3 QA/QC Reporting...............................................................................................................10 

5.0 Test Results....................................................................................................................................12 

6.0 Performance Summary...................................................................................................................13 

7.0 References .....................................................................................................................................14 
vi 

Figures

Figure 2-1. Ballast box installed on the outside of the test rig................................................................ 4 

Figure 2-2. Device installed inside the test rig....................................................................................... 4 

Figure 3-1. Schematic of Test Duct....................................................................................................... 5 

 

Tables

Table 2-1. Specifications of the AeroLogic Model AD24-4 ................................................................ 3 

 

Table 4-1. DQOs for Biological Aerosols..........................................................................................10 

Table 5-1. Inactivation Efficiency......................................................................................................12 

Table 5-2. Other Information for the AeroLogic Model AD24-4 Test................................................12 
vii 

Abbreviations/Acronyms 

A ampere 

ANSI American National Standards Institute 

ARTI Air-Conditioning and Refrigeration Technical Institute 

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers 

ASME American Society of Mechanical Engineers 

ATCC American Type Culture Collection 

B Bacillus

BG Bacillus atrophaeus (formerly B. subtilis var. niger and Bacillus globigii) 

BWA biological warfare agent 

°C degrees Celsius 

cfm cubic feet per minute 

CFU colony forming unit(s) 

cm centimeter(s) 

CV coefficient of variation 

DQO data quality objective 

EPA U.S. Environmental Protection Agency 

°F degrees Fahrenheit 

fpm feet per minute 

ft feet 

HVAC heating, ventilation and air-conditioning 

in. inch(es) 

J joule 

KCl potassium chloride 

m meter(s) 

mL milliliter(s) 

m micrometer(s) 

W microwatts(s) 

NEMA National Electrical Manufacturers Association 

nm nanometer(s) 

NHSRC National Homeland Security Research Center (EPA) 

QA quality assurance 

QC quality control 

OPC optical particle counter 

ORD Office of Research and Development (EPA) 

Pa pascal(s) 

PE performance evaluation 

PFU plaque forming unit(s) 
viii 

psig pounds per square inch gauge 

QMP quality management plan 

QSA quality system assessment 

RMS root mean square 

RTI Research Triangle Institute (RTI International) 

S Serratia 

sec second(s) 

TSA technical system assessment 

TTEP Technology Testing and Evaluation Program 

UV Ultraviolet; the C band is used for disinfection 

V volt(s) 

W watt(s) 
ix 

Executive Summary 

The U.S. Environmental Protection Agency’s (EPA’s) National Homeland Security Research Center 

(NHSRC) Technology Testing and Evaluation Program (TTEP) is helping to protect human health and 

the environment from adverse impacts resulting from acts of terror by carrying out performance tests on 

homeland security technologies. Under TTEP, RTI recently evaluated the performance of the Atlantic 

Ultraviolet Corporation AeroLogic Model AD24-4. The objective of testing the device was to evaluate 

its bioaerosol inactivation efficiency as a heating, ventilation and air-conditioning (HVAC) in-duct 

ultraviolet light system. 

The product was tested using a test plan approved by EPA, Test/QA Plan for Biological Inactivation 

Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners.

(1) The tests were conducted using three 

organisms, two bacteria (Bacillus atrophaeus and Serratia marcescens) and one bacterial virus (MS2). 

These organisms were selected because their sizes, shapes and susceptibility to UV inactivation make 

them reasonable surrogates for biological warfare agents (BWAs). Generally, vegetative bacteria are 

readily killed and bacterial spores are more difficult. To model use in an HVAC system, RTI used a test 

duct designed for testing filtration and inactivation efficiencies of aerosol, bioaerosol and chemical 

challenges. 

The bioaerosol inactivation efficiencies calculated for the three organisms were 0% for B. atrophaeus, 

99.8% for S. marcescens and 46% for MS2. The irradiance was measured as 480 W/cm2

 at 162 cm 

(63 in.) upstream from the lamps with an airflow of 0.93 m3

/sec (1970 cfm). There were 4 lamps that 

were burned in for 100 hours prior to measurements. 
1 

1.0 Introduction 

The U.S. Environmental Protection Agency’s (EPA’s) National Homeland Security Research Center 

(NHSRC) is helping to protect human health and the environment from adverse impacts resulting from 

intentional acts of terror. With an emphasis on decontamination and consequence management, water 

infrastructure protection, and threat and consequence assessment, NHRSC is working to develop tools 

and information that will help detect the intentional introduction of chemical or biological contaminants 

in buildings or water systems, the containment of these contaminants, the decontamination of buildings 

and/or water systems, and the disposal of material resulting from cleanups. 

NHSRC’s Technology Testing and Evaluation Program (TTEP) works in partnership with recognized 

testing organizations; with stakeholder groups consisting of buyers, vendor organizations, and 

permitters; and with the full participation of individual technology developers in carrying out 

performance tests on homeland security technologies. The program evaluates the performance of 

innovative homeland security technologies by developing test plans that are responsive to the needs of 

stakeholders, conducting tests, collecting and analyzing data, and preparing peer-reviewed reports. All 

evaluations are conducted in accordance with rigorous quality assurance (QA) protocols to ensure that 

data of known and high quality are generated and that the results are defensible. TTEP provides highquality information that is useful to decision makers in purchasing or applying the tested technologies. It 

provides potential users with unbiased, third-party information that can supplement vendor-provided 

information. Stakeholder involvement ensures that user needs and perspectives are incorporated into the 

test design so that useful performance information is produced for each of the tested technologies. 

UV lamps have been used to inactivate airborne microorganisms for many years. 

Much of the early work was directed at the control of very infectious microorganisms (particularly 

Mycobacterium tuberculosis, the causative agent of tuberculosis), often in medical facilities. 

Wavelengths within the short wave, or C band of UV light (UVC), were found to be the most effective 

germicidal light wavelengths. UVC usually is generated by use of UVC fluorescent lamps. These lamps 

use electrical discharge through low-pressure mercury vapor enclosed in a glass tube that transmits UVC 

light (primarily at the mercury wavelength of 253.7 nm). Because this wavelength has been found to be 

about the optimum for killing microorganisms, UVC from mercury lamps also is referred to as UVG to 

indicate that it is germicidal. UVG has been shown to inactivate viruses, mycoplasma, bacteria, and 

fungi when used appropriately. 

Numerous past studies of UVC to inactivate microorganisms have been conducted for a variety of 

purposes and with a variety of methods. No standard method exists for evaluating culturable bioaerosol 

inactivation by these devices. However, as part of the project entitled, “Defining the Effectiveness of 

UV Lamps Installed in Circulating Air Ductwork” funded by the Air-Conditioning and Refrigeration 

Technology Institute (ARTI), RTI developed a test method for measuring culturable bioaerosol 

inactivation efficiencies by UV lights.(2) This method was derived from earlier bioaerosol air cleaner 

test methods developed for determining the bioaerosol filtration efficiencies of various air cleaning 

devices including room air cleaners and duct-mounted ventilation filters.(3,4,5) These bioaerosol methods 

were based on RTI’s extensive experience in the development of particulate testing methods of various 

air-cleaning devices. 
2 

The current TTEP effort focuses on UV systems that are mounted in the HVAC ducting (in-duct UV 

light systems) and that operate on a “fly-through” basis. That is, they are designed to destroy 

bioaerosols in the flowing air stream as it passes through the device. This is distinguished from UV 

devices that are designed to treat specific surfaces within the HVAC system, in particular, the cooling 

coils and the condensate drain pan, to prevent biological growth on those surfaces. This program tested 

inactivation of airborne bioaerosols; inactivation of microorganisms on surfaces was not evaluated. 

The bioaerosol tests were conducted using three organisms, consisting of two bacteria (spore-forming 

Bacillus atrophaeus and the vegetative bacterium Serratia marcescens) and one bacterial virus (MS2) 

that cover the range of potential interest for biological warfare agent (BWA) applications. These 

organisms were selected because their sizes, shapes and susceptibility to UV inactivation make them 

reasonable surrogates for BWAs. Generally, vegetative bacteria are readily killed and bacterial spores 

are more difficult. The spore form of the bacteria Bacillus atrophaeus (formerly B. subtilis var. niger

and Bacillus globigii or BG) was used as the surrogate for gram-positive spore-forming bacteria. The 

BG spore is elliptically shaped with dimensions of 0.7 to 0.8 by 1 to 1.5 m. Serratia marcescens was 

used as the surrogate for rod-shaped gram-negative bacteria. S. marcescens is 0.5 to 0.8 by 0.9 to 2.0 

m. 

The bacterial virus (bacteriophage) MS2, having approximately the same aerosol characteristics as a 

human virus, was used as a surrogate for the viruses of similar and larger size and shape. Although the 

individual virus particles are in the 0.02 – 0.03 m size range, the test particle size for the virus tests 

spanned a range of sizes (polydispersed bioaerosol) in the micron range. This test was not designed to 

study the inactivation efficiencies for individual virus singlets; rather, it was designed to determine the 

inactivation efficiencies for virus particles as they are commonly found indoors. A representative 

challenge would be a polydispersed aerosol containing the bacteriophage because: 

$ The aerosols created from sneezing and coughing vary in size from < 1 to 20 m, but the largest 

particles settle out and only the smaller sizes remain in the air for extended periods for potential 

removal by an air cleaner; (6)

$ For some viruses (e.g., Coxsackie virus), few viruses have been found associated with the smallest 

particles; (7) and 

$ Nearly all 1 - 2 m particles are deposited in the respiratory tract, while larger particles may not be 

respired.
3 

2.0 Technology Description 

The information in this section was provided by the vendor and was not evaluated by RTI. 

AeroLogic Air Duct Disinfection Systems utilize germicidal lamps to protect personnel from potentially 

harmful airborne contaminants by effectively destroying airborne microbes including bacteria and 

viruses in new or existing duct systems. Desired bacteria kill rates of 90% for the average commercial 

installation or 98% kill rates (essential for hospitals and pharmaceutical laboratories) can be achieved 

using AeroLogic. Units are constructed of tough, corrosion-resistant Stainless Steel to insure long life. 

The AeroLogic Model AD24-4 system uses the 4-G24T6L slimline germicidal ultraviolet lamp. 

Table 2-1 provides information on the system as supplied by the vendor. Figures 2-1 and 2-2 provide 

views of the device as tested, installed in accordance with the manufacturer’s specifications. 

Table 2-1. Specifications of the AeroLogic Model AD24-4 

Attribute Specification

Total power for the lamp (watts) 25 W per lamp – 100 W Total (Lamp output only – does not

include ballast loss) 

Total UVC power for the lamp (watts) 8.5 W per lamp – 34 W Total (Output @ 254 nm at 100 hours

and 80 °F) 

Irradiance (output) of the lamp, give distance 

2 and other information (e.g., airflow) (W/cm )

82 W/cm2 @ 1m per lamp

2 Dosage (J/cm or W-s/cm2

) 

Ballast root mean square (RMS) voltage and 120 V 60 Hz .83 A Open Circuit: 775 RMS

current

Dimensions of the lamp 53.82 cm (21 3/16”) base face to base face

Dimensions of the ballast box Length - 43.8 cm (17 1/4 in.), width – 18.7 cm (7 3/8 in.),

depth – 10.6 cm (4 3/16 in.) 

Configuration 4-G24T6L germicidal lamps

Ballast box capable of mounting inside or outside of duct

Depth in duct approx. 57.8 cm (22 3/4 in.) 

Other lamp characteristics None 
4 

Figure 2-1. Ballast box installed on the

outside of the test rig. 

Figure 2-2. Device installed inside the test

rig. There are 4 lamps and 2 support rods. 

 

For more information on the AeroLogic Model AD24-4, contact: 

Mr. Hilary Boehme, Mr. Greg Boehme or Mrs. Ann M. Wysocki 

Atlantic Ultraviolet Corporation 

375 Marcus Boulevard 

Hauppauge, NY 11788 

Phone: 631-273-0500 

Fax: 631-273-0771 

Web: www.ultraviolet.com 
Figure 3-1. 

Schematic of 

Test Duct. UV 

system is placed in device section. 

3.0 Test Procedures 

3.1 Operation of the Test Duct 

The testing was conducted in the test duct shown schematically in Figure 3-1. The test section of the 

duct is 0.61 m by 0.61 m (24 in. by 24 in.). The locations of the major components, including the 

sampling probes, the device section (where the UV device is installed), and the aerosol generator (site of 

bioaerosol injection) are shown. The test duct is operated following procedures in the ANSI/ASHRAE 

(American National Standards Institute/American Society of Heating, Refrigerating and AirConditioning Engineers) Standard 52.2-1999, Method of Testing General Ventilation Air-Cleaning 

 (8) Devices for Removal Efficiency by Particle Size.

While Figure 3-1 shows the test duct without recirculation, during testing, the duct may be operated with 

or without recirculation. The decision for recirculation mode is based on building HVAC considerations. 

Because of the HEPA filters at the beginning and the end of the duct, the recirculation mode does not 

affect the test data as long as all other criteria are met. 

The air flow rate through the duct during this testing was 0.93 m3

/sec (1970 cfm). This flow creates a 

typical air velocity (492 fpm) in the duct, and has been used extensively in prior testing of air cleaning 

devices in this rig. The air temperature entering the device was approximately 23 °C. Air flow rate and 

temperature can have an impact on lamp performance, and the values used in this testing are consistent 

with vendor specifications. As explained in the VanOsdell and Foarde report,(2) lamps are designed for 

an optimal temperature, and either higher or lower values may lower the irradiance. 

Prior to testing the device, the UV lamps were operated for a standard 100-hr “burn-in” period. 

In a given run, one of the three challenge bioaerosols – prepared as described in Section 3.2 – was 

injected upstream of the device. A no-light test was performed with the UV lights turned off, to 

determine the microorganism loss that would occur simply as the result of deposition in the test duct, 

and as the result of kill caused by the physical rigors of flowing through the device. See Section 4.3 for 

the acceptable range of the penetration for this test. As discussed later, the performance of the device 

5 
6 

was then reported as the device’s efficiency in inactivating the organism with the light on, corrected to 

account for the loss of organisms observed in the absence of UV light. 

In addition to the measurement of the concentration of culturable organisms upstream and downstream 

of the device, other measurements that were made include: 

• The energy required to operate the unit, including the direct total power consumption by the lamp 

and ballast, the pressure drop across the device (impacting air handler requirements), and the 

temperature rise through the unit, if any (impacting cooling coil energy consumption). 

• A single measurement of the intensity of 254 nm UV radiation (W/cm2

) at a point 162 cm (63 in.) 

upstream from the lamps, to demonstrate that the lamps were functioning and to provide a test 

reference value for the laboratory for documentation purposes. 

3.2 Preparation and Generation of Bioaerosol Challenges 

The bioaerosol tests were conducted using three organisms, two bacteria (Bacillus atrophaeus and

Serratia marcescens) and one bacterial virus (MS2). The selection of the bioaerosols was discussed in 

Section 1. 

The microbial challenge suspensions were prepared by inoculating the test organism onto solid or into 

liquid media, incubating the culture until mature, wiping organisms from the surface of the pure culture 

(if solid media), and eluting them into sterile fluid to a known concentration to serve as a stock solution. 

The organism preparation was then diluted into sterile nebulizing fluid. The nebulizing fluid was 

composed of salts (buffering), peptone and antifoam (S. marcescens only). The composition of the 

nebulizing fluid should have provided a protective effect similar to organic matter (dirt, debris, etc.) for 

the S. marcescens and possibly the MS2 against the inactivation of the UVC. Based on the ARTI study, 

little or no effect was anticipated for the B. atrophaeus as spores were found to be relatively unaffected 

by protective factors.(2) The nebulizing fluid was quantified on trypticase soy agar to enumerate the 

bacteria. 

The bacteriophage challenge was prepared by inoculating a logarithmic phase broth culture of the host 

bacteria (E. coli) with bacteriophage and allowing it to multiply overnight or until the majority of the 

host bacteria were lysed (ruptured or broken down). The mixture was processed to collect and 

concentrate the bacteriophage. Then, the bacteriophage stock was filter sterilized (0.2 m) to remove the 

bacteria. The bacteriophage stock was used as the challenge aerosol. The concentration of the 

bacteriophage stock was approximately 1 x 109

 or higher plaque forming units (PFU)/mL. The virus 

assay used a standard double agar layer plaque assay, in which host cell Escherichia coli C3000 (ATCC 

15597) in the log phase of growth and serial dilutions of the MS2 virus stock (ATCC 15597-B1) were 

combined and top agar added and then poured onto bottom agar plates.(9) After incubation, at least 

overnight, at 37 °C, plaques (loci of infection) were counted against an opaque lawn of host cell E. coli

C3000.
The challenge organism suspensions were aerosolized using a Collison nebulizer (BGI, Waltham, MA) 

at 15 psi air pressure. The Collison nebulizer generated droplets with an approximate volume mean 

diameter of 2 m. The particle diameter after the water evaporated depended on the solids content of 

the suspension and the size of the suspended particles. Prior experience has shown that the bacterial 

organism aerosols generated by this procedure are primarily singlets. 

3.3 Sampling the Bioaerosols 

All the bioaerosols were collected in liquid impingers, AGI-4 (Ace Glass Inc., Vineland, NJ). Because 

exposure to UV radiation is a common environmental hazard, cells have developed a number of repair 

mechanisms to counteract UV-induced damage that must be considered when experimentally measuring 

UV effects. Collecting in impinger fluid maximized the collection of damaged organisms. After 

sampling, the impinger fluid was plated and incubated at appropriate times and temperatures for the test 

organism being used. To quantify the microbial counts, the plates were incubated at the appropriate 

temperature and time for the test organism (overnight to a week). Colonies or plaques were counted. 

7 

3.4 Bioaerosol Control Efficiency Calculation 

The efficiency of the device for inactivating airborne bioaerosols was then calculated as: 

(%) 1(100 ) (Equation 1) Ratecorrected Airborne Inactivation Efficiency =  Survival 

The calculation of the test organism survival rate (culturable transmission) was based on the ratio of the 

downstream to upstream culturable organism counts. To remove system bias, the Survival Rate was 

corrected by the results of the blank no-light transmission test. The blank no-light transmission rate 

(light was not turned on in the test duct) was calculated the same as the survival rate test, but using the 

culturable organism counts from the no-light tests. 

3.5 Average Dose of UV Delivered by the Device 

The equation used to describe the effect of UV on a single species population of airborne 

microorganisms is: 

 

(Equation 2) Nt/N0 = exp(- k · dose) 

where: 

 Nt = the number of microorganisms at time t, 

 N0 = the number of microorganisms at the start, 

 k = a microorganism-dependent rate constant, in cm2

/W·s. 

 

The fractional inactivation achieved by the device is (1-Nt/N0), as indicated in Equation 1. 

We calculate the dose by rearranging Equation 2 to yield 

(

k

ln NN

Dose 0t =  ) (Equation 3) 
8 

Mean dose was computed from Equation 3 using the values of Nt and N0 obtained with B. atrophaeus

and using the organism-specific value of k for this organism (1.6 x 10-4  0.3x 10-4

 cm

2

/W·s). B. 

atrophaeus was selected for determining dose based on earlier RTI measurements as discussed in 

Amendment 1 of the test plan. 

The UV dose calculated in this manner is the mean dose to a single organism having an “average” 

trajectory through the device. It is reported here as a characteristic of the device being tested. Dose is 

shown as a mean and a range plus standard deviation, reflecting the natural variation in a population of 

microorganisms. 
9 

4.0 Quality Assurance/Quality Control 

Quality assurance/quality control (QA/QC) procedures were performed in accordance with the program 

QMP and the test/QA plan for this evaluation. (10, 1) 

4.1 Equipment Calibration

4.1.1 Reference Methods 

As noted in Chapter 1, while reference methods were not available for determining the inactivation 

efficiency of the device, accepted methods developed and used in related work were used. Test 

specifications given in the appendices of the approved test/QA plan were derived from the related 

ASHRAE 52.2 method, with additional specifications and quality control checks relevant to this 

testing.(1,8)

4.1.2 Instrument Checks 

The AeroLogic Model AD24-4 was installed in the test duct, and operated and maintained according to 

the vendor’s instructions throughout the test. No maintenance was required during the test. 

4.2 Audits

4.2.1 Performance Evaluation Audit

No PE audits were performed during this test. 

4.2.2 Technical Systems Audit 

The RTI Quality Manager conducted a combined QSA/TSA to ensure that the technology evaluation 

was performed in accordance with the approved test/QA plan and the TTEP QMP. (1,10) Using a prepared 

checklist reflecting the test/QA plan, the RTI Quality Manager reviewed task systems as well as 

technology-specific sampling and analysis methods used, compared actual test procedures with those 

specified in the test/QA plan, and reviewed data acquisition and handling procedures.(1) Observations 

from this audit were documented and submitted to the RTI Task Manager. No significant findings were 

noted in this assessment that might impact the quality of the evaluation results. The records concerning 

the TSA are permanently stored with the RTI Task Manager. 

The EPA Quality Manager conducted a combined QSA/TSA to independently assess conformance to 

the approved test/QA plan of project activities.(1) No significant findings were noted in this assessment 

that might impact the quality of the evaluation results. Minor recommendations were made and are 

being implemented. 

4.2.3 Data Quality Audit

At least 10% of the data acquired during the evaluation was audited by the RTI Quality Manager who 

traced the data from the initial acquisition, through reduction and statistical analysis, to final reporting, 
to ensure the integrity of the reported results. All calculations performed on the data undergoing the 

audit were checked. This activity is summarized in a technology-specific report to the RTI Task 

Manager. 

4.3 QA/QC Reporting 

Each assessment and audit was documented in accordance with the test/QA plan.(1) Once the assessment 

report was prepared, the RTI Task Manager ensured that a response was provided as appropriate. For 

this technology evaluation, no significant findings were noted in any assessment or audit, and no followup corrective action was necessary. 

The testing followed quality assurance and quality control requirements as given in the test/QA plan. 

The RTI Quality Assurance Manager reviewed the test results and the quality control data and 

concluded that the data quality objectives as shown in Table 4-1 and in Amendment 1 of the test/QA 

plan were attained. 

Table 4-1. DQOs for Biological Aerosols 

Parameter Frequency and

description

Control Limits

Minimum upstream

counts for samplers

Each efficiency test. Minimum of 10 CFUa/plate or PFUb/plate

Maximum counts for

samplers 

Each efficiency test. Maximum of 500 CFU/plate or 800 PFUb/plate

100% Penetration

(no light) 

(correlation test) 

Performed at least once

per test sequence per

organism.

Test 

Organism 

B. atrophaeus 

S. marcescens 

 Acceptable

Penetration Range

 0.85 to 1.15 

 0.80 to 1.20

MS2 0.75 to 1.25

Upstream CFUs Each test. Statistical check

of data quality. 

CVc # 0.25 

Upstream PFUs Each test. Statistical check

of data quality. 

CVc # 0.35 

a

 CFU

b

 PFU c

 CV

= 

= 

= 

colony forming units

plaque forming unit

coefficient of variance 



Data quality objectives (DQOs) are qualitative and quantitative statements designed to ensure that the 

type, quality, and quantity of data used are appropriate for the intended application. In addition, the 

minimum and maximum upstream counts help to ensure that the challenge concentration of each 

organism entering the UV device remains at an acceptably steady value that is sufficiently low such that 

device performance should be independent of the concentration at the test conditions used in this study. 

10 
11 

5.0 Test Results 

The bioaerosol inactivation efficiency results, derived using Equation 1, are given in Table 5-1. Table 5-

2 provides other information about the UV system. 

Table 5-1. Inactivation Efficiency 

Test organism

Spore form of bacteria

(B. atrophaeus)

Vegetative bacteria

(S. marcescens)

Bacterial virus 

(MS2 bacteriophage)

Inactivation 

efficiency, (UV light

on) %

0 99.8a 46 

a – the value 99.8 represents a 95% confidence limit for S.

measured. 

marcescens. There were no downstream counts

Table 5-2. Other Information for the AeroLogic Model AD24-4 Test

Attribute Measured or Calculated Values 

Test duct operating conditions

Air flow rate 0.93 m3/sec (1970 cfm)

Inlet and outlet temperature Upstream 23.0 °Ca (73.5°F) , Downstream

23.2 °Ca

 (73.8 °F)

UV exposure conditions provided by device

Mean dosage calculated from Equation 3 and range resulting

from standard deviation of the k value 

2 295 (249 - 363) W-s/cm

A single irradiance measurement at 254 nm 480 

from

2 W/cm at 162 cm (63 in.) upstream

the lamps at 0.93 m3

/sec (1970 cfm)

Measures of energy consumption by the unit

Power consumed by the lamps/ballasts and by any 

 ancillary equipment required by the vendor 

 94 W 

Pressure drop across the device < 8 Pab (0.03 in. H20) 

Air temperature rise through the device 0.2 °Ca (0.3 °F) 

a – the accuracy of the thermometers are 0.5 °C; therefore, temperature variations below that are not

necessarily significant.

b – the pressure drop was less than the maximum allowable pressure drop measurement for an empty test

(8) section as specified in ANSI/ASHRAE 52.2-1999.
12 

6.0 Performance Summary 

This verification report addresses the inactivation efficiency performance (Table 5-1) for the Atlantic 

Ultraviolet Corporation AeroLogic Model AD24-4 UV light system that operates in an HVAC system. 

Other measures are given in Table 5-2. Users may wish to consider other performance parameters such 

as service life and cost when selecting a UV light system for their application. 

The bioaerosol inactivation efficiencies calculated for the three organisms were 0% for B. atrophaeus, 

99.8% for S. marcescens and 46% for MS2. The irradiance was measured as 480 W/cm2

 at 162 cm 

(63 in.) upstream from the lamps with an airflow of 0.93 m3

/sec (1970 cfm). There were 4 lamps that 

were burned in for 100 hours prior to measurements. The spore form of the bacteria B. atrophaeus is

more resistant to being killed by UV than the vegetative bacteria S. marcescens. 
13 

7.0 References 

1. RTI. 2005. Test/QA Plan for Biological Inactivation Efficiency by HVAC In-Duct Ultraviolet Light 

Air Cleaners. Research Triangle Institute, Research Triangle Park, NC. 

2. VanOsdell, D. and K. Foarde. 2002. Final Report ARTI-21CR/610-40030-01 Project -Defining the 

Effectiveness of UV Lamps Installed in Circulating Air Ductwork, Air-Conditioning and 

Refrigeration Technology Institute, 4100 N. Fairfax Drive, Suite 200, Arlington, Virginia 22203. 

 http://www.arti-21cr.org/research/completed/finalreports/40030-final.pdf

3. Foarde, K. and J. Hanley. 2001. Determine the Efficacy of Antimicrobial Treatments of Fibrous Air 

Filters. ASHRAE Transactions. Volume 107, Part 1. 156-170. 

4. Foarde, K.K. and J.T. Hanley. 1999. A New Laboratory Method for Measuring the Bioaerosol 

Filtration Efficiency of Air Cleaners. Proceedings: 1999 Air Filtration Conference: Fall Topical 

Conference pp. 47-54. 

5. Foarde, K.K., J.T. Hanley, D.S. Ensor, and P.F. Roessler. 1999. Development of a Method for 

Measuring Single-Pass Bioaerosol Removal Efficiencies of a Room Air Cleaner. Aerosol Science 

and Technology. 30: 223-234. 

6. Knight, V. 1973. Viral and Mycoplasmal Infections of the Respiratory Tract, Lea & Febiger, 

Philadelphia, PA. 

7. Buckland, F.E., and Tyrell, D.A.S. 1962. Loss of Infectivity on Drying Various Viruses, Nature

195: 1063-1064. 

8. ANSI/ASHRAE (American National Standards Institute/American Society of Heating, Refrigerating 

and Air-Conditioning Engineers). 1999. ANSI/ASHRAE Standard 52.2-1999, Method of Testing 

General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size, Section 5.16.2, 

Atlanta, GA. 

9. Adams, M.G. (1959). Bacteriophages. Interscience, New York. 

10. Battelle. Quality Management Plan (QMP) for the Technology Testing and Evaluation Program 

(TTEP), Version 1, January 2005. Columbus, OH.