Environmental Technology Verification
Biological Inactivation Efficiency by HVAC
In-Duct Ultraviolet Light Systems
American Ultraviolet Corporation, DC24-6-120
Prepared by
Research Triangle Institute
HRTI
INTERNATIONAL
Under a Cooperative Agreement with the
U.S. Environmental Protection Agency
&EPA
EIV EW ET
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American Ultraviolet Corporation, DC24-6-120 Duct Sterilizer
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM ,O
EW
U.S. Environmental Protection Agency
HRTI
INTERNATIONAL
ETV Joint Verification Statement
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
COMPANY:
ADDRESS:
WEB SITE:
E-MAIL:
GENERAL VENTILATION AIR CLEANERS
BIOLOGICAL INACTIVATION EFFICIENCY BY
HVAC IN-DUCT ULTRAVIOLET LIGHT
SYSTEMS
DC24-6-120
American Ultraviolet Corporation
212 S Mount Zion Road
Lebanon, IN 46052
PHONE:
FAX:
800-288-9288,
ext. 201
765-483-9525
http://www.americanultraviolet.com
mstinesfoiauvco. com
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative or improved environmental
technologies through performance verification and dissemination of information. The goal of the ETV
Program is to further environmental protection by accelerating the acceptance and use of improved and
cost-effective technologies. ETV seeks to achieve this goal by providing high-quality, peer-reviewed data
on technology performance to those involved in the design, distribution, financing, permitting, purchase,
and use of environmental technologies.
ETV works in partnership with recognized standards and testing organizations; stakeholder groups, which
consist of buyers, vendor organizations, permitters, and other interested parties; and with the full
participation of individual technology developers. The program evaluates the performance of innovative
technologies by developing test plans that are responsive to the needs of stakeholders, conducting field or
laboratory tests (as appropriate), collecting and analyzing data, and preparing peer-reviewed reports. All
evaluations are conducted in accordance with rigorous quality assurance protocols to ensure that data of
known and adequate quality are generated and that the results are defensible.
The Air Pollution Control Technology Verification Center (APCT Center) is operated by RTI
International (RTI), in cooperation with EPA's National Risk Management Research Laboratory. The
S-l
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American Ultraviolet Corporation, DC24-6-120 Duct Sterilizer
APCT Center conducts verifications of technologies that clean air in ventilation systems, including in-
duct ultraviolet (UV) light systems. This verification statement provides a summary of the test results for
the American Ultraviolet Corporation DC24-6-120 Duct Sterilizer.
VERIFICATION TEST DESCRIPTION
All tests were performed in accordance with RTFs "Bioaerosol Inactivation Efficiency by HVAC In-Duct
Ultraviolet Light Air Cleaner", a supplement to "Test/Quality Assurance Plan for Biological and Aerosol
Testing of General Ventilation Air Cleaners" which was approved by EPA. Testing for biological
inactivation was performed using three organisms - two bacteria (Bacillus atrophaeus and Serratia
marcescens) and one bacterial virus (MS2). To model use in a heating, ventilation and air-conditioning
(HVAC) system, RTI used a test duct designed for testing filtration and inactivation efficiencies of
aerosol, bioaerosol, and chemical challenges.
The testing was conducted in the test duct operated following procedures in the ANSI/ASHRAE
(American National Standards Institute/American Society of Heating, Refrigerating and Air-Conditioning
Engineers) Standard 52.2-1999, Method of Testing General Ventilation Air-Cleaning Devices for
Removal Efficiency by Particle Size. 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 fbm) 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. Prior to testing the device, the UV
lamps were operated for a standard 100-hr "burn-in" period.
There are separate runs for each of the three challenge bioaerosols which were injected upstream of the
device. The upstream challenge was ~ 2 x 104 CPU or PFU/ft3. 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. The performance of the device 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.
Additional secondary measurements included:
• 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 (uW/cm2) at a point 161 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.
Verification testing of the American Ultraviolet Corporation DC24-6-120 began on July 31, 2007 at the
test facilities of RTI and was completed on August 21, 2007.
VERIFIED TECHNOLOGY DESCRIPTION
The American Ultraviolet Company's DC24-6-120 is part of the DC Series of in-line duct sterilizers that
are designed to install into air duct sections to position high output UVC (short-wave ultraviolet radiation,
in the "C" band - 200 to 280 nanometers) lamp(s) perpendicular to passing airflow for "pass-by" air
sterilization purposes as well as surface sterilization. The ballast enclosure mounts directly to the duct
S-2
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American Ultraviolet Corporation, DC24-6-120 Duct Sterilizer
exterior with lamp(s) protruding into the duct section through a cutout in the duct wall. Type 304 stainless
steel construction is utilized for long life. Outdoor ballast enclosures are available as an option. The
SBL415 High Output UVC Lamp is used in the system.
VERIFICATION RESULTS
The American Ultraviolet Corporation DC24-6-120 achieved the biological inactivation efficiency tests
presented in Table 1.
Table 1. Inactivation Efficiency, %
Inactivation
efficiency (UV
light on), %
Spore form of
bacteria
(B. atrophaeus)
98
Vegetative bacteria
(S. marcescens)
>99.5a
Bacterial virus
(MS2
bacteriophage)
99
a - the value 99.5 represents a 95% confidence limit for S. marcescens. There were no downstream counts
measured.
The irradiance was measured as 6290 (iW/cm2 at 161 cm (63 in.) upstream from the lamps with an
airflow of 0.93 m3/sec (1970 cfm). The mean dosage was calculated as 23,600 (iW-s/cm2 with a range of
19,900 - 29,000 (iW-s/cm2. The system had six 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 light
(irradiation) than the vegetative bacteria S. marcescens.
The APCT Center's quality manager reviewed the test results and the quality control data and concluded
that the data quality objectives given in the approved test/QA plan were attained.
This verification statement addresses the biological inactivation efficiency. Users of this technology may
wish to consider other performance parameters such as service life and cost when selecting an in-duct UV
system for bioaerosol control.
Original signed by Sally Gutierrez. 01/17/08
Sally Gutierrez Date
Director
National Risk Management Research Laboratory
Office of Research and Development
United States Environmental Protection Agency
Original signed by Andrew Trenholm.
Andrew R. Trenholm
Director
APCT Center
RTI International
01/10/08
Date
NOTICE: ETV verifications are based on an evaluation of technology performance under specific, predetermined
criteria and the appropriate quality assurance procedures. EPA and RTI make no express or implied warranties as to
the performance of the technology and do not certify that a technology will always operate as verified. The end user
is solely responsible for complying with any and all applicable federal, state, and local requirements. Mention of
commercial product names does not imply endorsement.
S-3
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Environmental Technology Verification
Biological Inactivation Efficiency by HVAC
In-Duct Ultraviolet Light Systems
American Ultraviolet Corporation, DC24-6-120
Prepared by:
Research Triangle Institute
Engineering and Technology Unit
Research Triangle Park, NC 27709
EPA Cooperative Agreement CR 831911-01
EPA Project Manager
Michael Kosusko
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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NOTICE
This document was prepared by RTI International* (RTI) with partial funding from Cooperative
Agreement No. CR 831911-01 with the U.S. Environmental Protection Agency (EPA). The document
has been subjected to RTI/EPA's peer and administrative reviews and has been approved for publication.
Mention of corporation names, trade names, or commercial products does not constitute endorsement or
recommendation for use of specific products.
FOREWORD
The Environmental Technology Verification (ETV) Program, established by the U.S. Environmental
Protection Agency (EPA), is designed to accelerate the development and commercialization of new or
improved technologies through third-party verification and reporting of performance. The goal of the
ETV Program is to verify the performance of commercially ready environmental technologies through the
evaluation of objective and quality-assured data so that potential purchasers and permitters are provided
with an independent and credible assessment of the technology that they are buying or permitting.
The Air Pollution Control Technology Verification Center (APCT Center) is part of the EPA's ETV
Program and is operated as a partnership between RTI International (RTI) and EPA. The center verifies
the performance of commercially ready air pollution control technologies. Verification tests use approved
protocols, and verified performance is reported in verification statements signed by EPA and RTI
officials.
AVAILABILITY OF REPORT
Copies of this verification report are available from
• Research Triangle Institute
Engineering and Technology Unit
PO Box 12194
Research Triangle Park, NC 27709-2194
• U.S. Environmental Protection Agency
Air Pollution Prevention and Control Division, E343-02
109 T.W. Alexander Drive
Research Triangle Park, NC 27711
Web site: htto://www.epa.gov/etv/verifiedtechnologies.html
RTI International is a trade name of Research Triangle Institute.
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TABLE OF CONTENTS
ETV Joint Verification Statement S-l
Notice ii
Foreword ii
Availability of Report ii
Table of Contents iii
Acronyms/Abbreviations iv
Acknowledgments v
1.0 Introduction 1
2.0 Technology Description 2
3.0 Test Design and Procedure 3
4.0 Quality Assurance/Quality Control 6
5.0 Test Results 8
6.0 Limitations and Applications 9
7.0 References 9
FIGURES
Figure 2-1. Ballast box installed on the outside of the test rig 2
Figure 2-2. Device installed inside the test rig 2
Figure 3-1. Schematic of test duct 3
TABLES
Table 2-1. Vendor-Supplied Specifications of the DC24-6-120 2
Table 4-1. DQOs for Biological Aerosols 7
Table 5-1. Inactivation Efficiency 8
Table 5-2. Other Information for the DC24-6-120 8
in
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ACRONYMS/ABBREVIATIONS
A
ANSI
APCT Center
ARTI
ASHRAE
ASME
B
BG
C
cfm
CPU
cm
CV
DQO
E
EPA
ETV
F
fpm
HEPA
HVAC
in.
J
L
m
mm
mL
min
nm
QA
QC
QMP
QSA
Pa
PFU
psig
RMS
RTI
S
s
TSA
TTEP
UV
UVC
amp(s)
American National Standards Institute
Air Pollution Control Technology Verification Center
Air-Conditioning and Refrigeration Technology Institute, Inc.
American Society of Heating, Refrigerating and Air-Conditioning Engineers
American Society of Mechanical Engineers
Bacillus
Bacillus atrophaeus (formerly B. subtilis var niger and Bacillus globigii)
Celsius
cubic feet per minute
colony forming unit(s)
centimeter
coefficient of variance
data quality objective
Escherichia
U.S. Environmental Protection Agency
environmental technology verification
Fahrenheit
feet per minute
high efficiency particulate air
heating, ventilation and air conditioning
inch(es)
joule (s)
liter(s)
meter(s)
millimeter(s)
milliliter(s)
minute(s)
micrometer(s)
nanometer(s)
quality assurance
quality control
quality management plan
quality system audit
pascal(s)
plaque forming unit(s)
pounds per square inch gauge
root mean square
Research Triangle Institute
Serratia
second(s)
technical systems audit
Technology Testing and Evaluation Program
ultraviolet
Short-wave ultraviolet radiation, in the "C" band (200 to 280 nanometers)
IV
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ACKNOWLEDGMENTS
The authors acknowledge the support of all of those who helped plan and conduct the verification
activities. In particular, we would like to thank Mike Kosusko, EPA's Project Manager, and Paul Groff,
EPA's Quality Assurance Manager, both of EPA's National Risk Management Research Laboratory in
Research Triangle Park, NC. We would also like to acknowledge the assistance and participation of
American Ultraviolet Corporation personnel who supported the test effort.
For more information on the DC24-6-120, contact:
Mr. Meredith C. Stines, President/CEO
American Ultraviolet
212 S Mount Zion Road
Lebanon, IN 46052
Phone: 800-288-9288 ext.201
Fax: 765-483-9525
mstines@auvco.com
www. americanultraviolet. com
For more information on RTFs ETV program, contact
Debbie Franke
Research Triangle Institute
PO Box 12194
Research Triangle Park, NC 27709-2194
Telephone: (919) 541-6826
Email: dlf@rti.org
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1.0 INTRODUCTION
This report reviews testing performed for bioaerosol inactivation efficiency of the American Ultraviolet
Company's DC24-6-120. Environmental Technology Verification (ETV) Program testing of this
technology/product was conducted by RTFs Air Pollution Control Technology Verification Center
(APCT Center) from July 31 to August 21, 2007. The testing followed the Bioaerosol Inactivation
Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners, Supplement to the APCT Center Test/QA
Plan for Biological and Aerosol Testing of General Ventilation Air Cleaners1.
Section 2 presents a description of the American Ultraviolet Company's DC24-6-120. Section 3
documents the procedures and methods used for the test and the conditions over which the test was
conducted. Section 4 provides information on the quality assurance (QA) and quality control (QC). The
results of the test are summarized and discussed in Section 5 with limits and applications in Section 6.
There is a performance summary in Section 7 and references in Section 8.
This report contains summary information and data from the test as well as the verification statement.
Complete documentation of the test results is provided in a separate data package and audit of data quality
report. These reports include the raw test data from product testing and supplemental testing, equipment
calibrations results, and QA/QC activities and results. Complete documentation of QA/QC activities and
results, raw test data, and equipment calibrations results are retained in RTFs files for seven years.
This ETV testing focuses on ultraviolet (UV) light systems that are mounted in the heating, ventilation
and air conditioning (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 tests inactivation of airborne bioaerosols; inactivation of microorganisms
on surfaces is not evaluated.
The bioaerosol tests were conducted using three organisms, consisting of two bacteria (spore-form of
Bacillus atrophaeus and the vegetative bacterium Serratia marcescens) and one bacterial virus (MS2) that
cover the range of potential interest for indoor air quality applications. These organisms were selected
because of their representative sizes and shapes, and susceptibility to UV inactivation. 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 to
represent gram-positive spore-forming bacteria. The BG spore is elliptically shaped with dimensions of
0.7 to 0.8 by 1 to 1.5 (im. Serratia marcescens was used to represent rod-shaped gram-negative bacteria.
S. marcescens is 0.5 to 0.8 by 0.9 to 2.0 (im.
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 (im 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 (im, 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;2
1
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• For some viruses (e.g., Coxsackie virus), low numbers of viruses have been found associated with the
smallest particles;3 and
• Nearly all 1 - 2 (im particles are deposited in the respiratory tract, while larger particles may not be
respired.
2.0 TECHNOLOGY DESCRIPTION
The American Ultraviolet Company's DC24-6-120 is part of the DC Series in-line duct sterilizers that are
designed to install into air duct sections to position high output UVC (short-wave ultraviolet radiation, in
the "C" band - 200 to 280 nanometers) lamp(s) perpendicular to passing airflow for "pass-by" air
sterilization purposes as well as surface sterilization. The ballast enclosure mounts directly to the duct
exterior with lamp(s) protruding into the duct section through a cutout in the duct wall. Type 304 stainless
steel construction utilized for long life. Outdoor ballast enclosures are available as an option. The SBL415
High Output UVC Lamp is used in the system.
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. Vendor-Supplied Specifications of the DC24-6-120
Attribute
Total power for the lamp (watts)
Total UVC power for the lamp (watts)
Irradiance (output) of the lamp, give distance
and other information (e.g., airflow) (W/cm2)
Dosage (J/cm2 or W-s/cm2)
Ballast root mean square (RMS) voltage and
current
Dimensions of the lamp
Dimensions of the ballast box
Configuration
Other lamp characteristics
Specification
60 watts per lamp, total of 360 watts
Estimated 22 UVC watts per lamp
1262|o,W/cm2 at 1 meter distance (total)
[400 fpm, 7.2 °C (45 °F) airflow]
N/A
Available as 120/230/277 VAC
3.45/2.10/1.80 amps total per 6-lamp fixture
534mm / 53.4 cm (21.03 in.) arc Length
61 cm (24 in.) long x 15.2 cm (6 in.) wide x 11.6 (4.56 in.)
tall
six-lamp unit w/ ballasts mounted in enclosure located out of
airflow
N/A
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Figure 2-1. Ballast box installed on the
outside of the test rig (on right). The
device is also visible.
Figure 2-2. Device installed inside the test
rig. There are six lamps and three support rods.
3.0 TEST DESIGN AND 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 Air-Conditioning Engineers)
Standard 52.2-1999, Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency
by Particle Size. 4
Exhaust
to
Room
Outlet Filter Bank
ASME
Nozzle
Downstream Mixer
Room
Air
1 Biological
1 1 Sampling
>
s
^
\
^ ^ '
T
>
Inlet
| @ l ^ ^
f f \ 1
Filter Upstream Ssft,
1
Device Backup
Section Filter
Bank I Mixer 1^1 lusf 9 vv[?enx
' " Dust-loading)
Aerosol Biological
Generator Samp
ina
Flow Control
Valve
Figure 3-1. Schematic of test duct. UV system is placed in device section.
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 FfVAC considerations.
Because of the high efficiency particulate air (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.
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The air flow rate through the duct during this testing was 0.93 mVsec (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 (2002)5 report for the Air-
Conditioning and Refrigeration Technology Institute (ARTI), 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.
There are separate runs for each of the three challenge bioaerosols which are prepared as described in
Section 3.2 and injected upstream of the device. The upstream challenge was ~ 2 x 104 CPU or PFU/ft3.
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 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, there were secondary measurements that were not included in the verification statement. These
include:
• 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 (uW/cm2) at a point 161 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 as described in the test/QA plan supplement 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 VanOsdell
and Foarde (2002)5 report, little or no effect was anticipated for the B. atrophaeus as spores were found to
be relatively unaffected by protective factors. 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
4
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bacteria (E. coif) 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 \am) 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 coll 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.6 After incubation, at least overnight, at 37 °C, plaques (loci of
infection) were counted against an opaque lawn of host cell E. coll 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 (im. 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., Vine land, 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.
3.4 Bioaerosol Control Efficiency Calculation
The efficiency of the device for inactivating airborne bioaerosols was then calculated as:
Airborne Inactivation Efficiency (%) = 100 (1 — Survival Ratecorrecte(j) (Equation 1)
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:
Nt/N0 = exp(-k • dose) (Equation 2)
where:
Nt = the number of microorganisms at time t,
NO = the number of microorganisms at the start,
k = a microorganism-dependent rate constant, in cm2/(iW-s. The k value includes a standard
deviation because there is not a single microorganism, but a population.
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The fractional inactivation achieved by the device is (1 - Nt/N0), as indicated in Equation 1 and where
is the survival rate.
We calculate the dose by rearranging Equation 2 to yield
In (N t /N 0 ) (Equation 3)
Dose = - -
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 cm2/(iW-s). B. atrophaeus
was selected for determining dose based on earlier RTI measurements.
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 (mean standard deviation), reflecting the natural variation in a population of
microorganisms and the spread of the measured values.
4.0 QUALITY ASSURANCE/QUALITY CONTROL
4.1 QUALITY ASSURANCE
Quality assurance/quality control (QA/QC) procedures were performed in accordance with the APCT
Center and ETV quality management plans (QMPs) and the test/QA plan for this technology.(7> 8>!)
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.(1'4)
4.1.2 Instrument Checks
The DC24-6-120 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. The test rig and
measurement instruments were checked according to the appendices of the approved test/QA plan and
supplement.
4.2 Audits
4.2.1 Performance Evaluation Audit
No performance evaluation audits were performed during this test.
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4.2.2 Technical Systems Audit (TSA)
No internal or EPA audit was performed during this APCT testing although one is planned for the next
product to be tested. During RTFs Technology Testing and Evaluation Program (TTEP) which evaluated
similar UV light systems, both Gene Tatsch9, then APCT Center quality manager, and Shirley Wasson10,
then EPA quality manager, performed combined quality system audits (QSAs)/TSAs of RTFs filter test
facility. No significant findings were noted in those assessments that might have impacted the quality of
the TTEP results. Minor recommendations were made and were implemented. The current test is being
performed using the same equipment and the same methods as during the TTEP testing.
4.2.3 Data Quality Audit
At least 10% of the data acquired during the verification testing of the device was audited by Gene Tatsch
as a representative of the APCT Center quality manager, Gary Eaton. Gene 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.
4.3 QA/QC Reporting
Each assessment and audit was documented in accordance with the test/QA plan.1-1-1 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 follow-up
corrective action was necessary. The testing followed quality assurance and quality control requirements
as given in the test/QA plan. The APCT Center quality manager reviewed the test results and the quality
control data and concluded that the data quality objectives as shown in Table 4-1 were attained.
Table 4-1. DQOs for Biological Aerosols
Parameter
Minimum upstream counts
for samplers
Maximum counts for
samplers
100% Penetration
(no light)
(correlation test)
Upstream CPUs
Upstream PFUs
Frequency and description
Each efficiency test.
Each efficiency test.
Performed at least once per test
sequence per organism.
Each test. Statistical check of
data quality.
Each test. Statistical check of
data quality.
Control Limits
Minimum of 10 CFUa/plate or PFUb/plate
Maximum of 500 CFU/plate or 800
PFU/plate
Test Acceptable
Organism Penetration Range
B. atrophaeus 0.85 to 1.15
S. marcescens 0.80 to 1.20
MS2 0.75 to 1.25
CVC < 0.25
CV<0.35
a CPU = colony forming units
b PFU = plaque forming unit
0 CV = coefficient of variance
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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.
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, %
Inactivation
efficiency (UV
light on), %
Spore form of
bacteria
(B. atrophaeus)
98
Vegetative bacteria
(S. marcescens)
> 99.5a
Bacterial virus
(MS2 bacteriophage)
99
a - the value 99.5 represents a 95% confidence limit for S. marcescens. There were no downstream counts
measured.
Table 5-2. Other Information for the DC24-6-120
Attribute
Test duct operating conditions
Air flow rate
Inlet and outlet temperature
UV exposure conditions provided by device
Mean dosage calculated from Equation 3 and range resulting
from standard deviation of the k value
A single irradiance measurement at 254 nm
Measures of energy consumption by the unit
Power consumed by the lamps/ballasts and by any
ancillary equipment required by the vendor
Pressure drop across the device
Air temperature rise through the device
Measured or Calculated Values
0.93 nrVsec (1970 cfm)
Upstream 23.1 °Ca (73.6°F) , Downstream
23.8 °Ca (74.8 °F)
23,600 (19,900 - 29,000) (iW-s/cm2
6290 (iW/cm2 at 161 cm (63 in.) upstream
from the lamps at 0.93 mVsec (1970 cfm)
488 W
< 27.9 Pa (0.1 12 in. H20)
0.7°C(1.2°F)
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6.0 LIMITATIONS AND APPLICATIONS
This verification report addresses the inactivation efficiency performance (Table 5-1) for the American
Ultraviolet Corporation DC24-6-120 ultra-violet 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.
7.0 REFERENCES
1. RTI. 2007. Test/QA Plan for Biological and Aerosol Testing of General Ventilation Air Cleaners, and
Supplement Bioaerosol Inactivation Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners.
Research Triangle Institute, Research Triangle Park, NC.
2. Knight, V. 1973. Viral and Mycoplasmal Infections of the Respiratory Tract, Lea & Febiger,
Philadelphia, PA.
3. Buckland, F.E., and Tyrell, D.A.S. 1962. Loss of Infectivity on Drying Various Viruses, Nature 195:
1063-1064.
4. 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.
5. 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
6. Adams, M.G. (1959). Bacteriophages. Interscience, New York.
7. RTI. 2005. Quality Management Plan for Verification Testing of Air Pollution Control Technology,
Revision 2.2, Research Triangle Park, NC. http://www.epa.gov/etv/pubs/APCT QMP 0205.pdf
8. U.S. EPA. 2002. Environmental Technology Verification Program Quality Management Plan,
EPA/600/R-03/021, U.S. EPA, Cincinnati, OH, 2002.
http://www.epa.gov/etv/pubs/ETV 02 QMP.pdf
9. Tatsch, C. Eugene. 2005. Assessment of RTI's TTEP Project, Research Triangle Institute, Research
Triangle Park, NC.
10. Wasson, Shirley. 2005. Quality and Technical Systems Audits for Technology Testing and Evaluation
Program Bioaerosol Inactivation Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners, US
EPA, Research Triangle Park, NC. Laura Nessley and David Proffitt from Arcadis G&M participated
in the audit with Ms. Wasson.
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