EPA/600/A-
UPDATE ON EPA'S AIR DUCT CLEANING RESEARCH ACTIVITIES
Russell N. Kulp
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
[ph: 919/541-7980, fax: 919/541-2157, email: ]
INTRODUCTION
The U.S. Environmental Protection Agency's (EPA's) Office of Research and
Development (ORD) and the National Air Duct Cleaners Association, Inc. (NADCA) are actively
engaged in research that is designed to focus on important issues related to source
management/control and indoor air quality (IAQ) and their relationship to the air duct cleaning
(ADC) industry (Kulp 1995).
Utilizing the authority granted under the Federal Technology Transfer Act and a contract
called a Cooperative Research and Development Agreement (CRADA), the ORD and NADCA
have embarked upon a research program aimed at increasing our knowledge about the application
and effectiveness of ADC as a technique to control heating, ventilating, and air-conditioning
(HVAC) system sources, primarily particulate matter and microbial growth, and as a way to
improve IAQ while conserving energy.
ADC involves the physical removal of particulate matter and debris from air distribution
systems and their associated components such as fans, fan housings, heating and cooling coils, and
control devices (NADCA 1992). In recent years there has been a dramatic increase in the number
of companies offering ADC services for both commercial and residential systems (Future
Technology Surveys 1993).
One possible reason for this increase may be increased public awareness of the effects
associated with poor IAQ, that HVAC systems, which were once considered to be a part of the
solution to poor IAQ, are now known to be a potential major contributor of indoor pollutants
(Batterman and Burge 1995).
In any event, building owners are routinely advised to take an active role in maintaining
mechanical systems hygiene (EPA/NIOSH 1991); however, many claims have been made about
the benefits of ADC. Claims have been made that ADC can improve IAQ by reducing levels of
dust and microbial growth. Health benefits include relief from allergies and asthma. ADC can
save energy cost is another claim.
Perhaps compounding the problem is that very little published research data regarding
ADC effectiveness or impact are available, and the data that are available are not easily
interpreted and in some cases are contradictory.
A study conducted by the Florida International University (Ahmad, et al. 1994) found a
reduction in respirable particles and in bioaerosol concentrations following ADC, but no change in
submicrometer particle concentrations. Particle concentrations in the study houses were found to
be higher during cleaning than before or after. Another field study investigating ADC in a
computer facility and its impact on airborne particle counts during cleaning (Cochrane 1995)
1
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concluded that, with appropriate environmental safeguards and equipment, ADC will not
necessarily increase the airborne particulates in the occupied space.
A recent Canadian study (Fugler and Auger 1994) conducted in residences concluded that
ADC did not reduce the levels of circulating dust in residences and, in at least one house, a dust
cloud was liberated after cleaning. The same study also reported finding no improvement in fan
pressure drop or duct flow rates after ADC. NADCA (Fellman 1994) has pointed out some
limitations of the work reported in that study. Another study conducted in Japan concluded that
ADC can reduce levels of TVOCs (total volatile organic compounds) and perceived odors
(Ishikawa, et al. 1996).
ADC, at least in relatively dirty ventilation systems, is thought to improve energy
efficiency of the heating and air-conditioning (HAC) system (Carl and Smilie 1991). Another
Japanese study concluded that the cleaning process is an effective means of reducing deposits in
ductwork (Ito, et al. 1996).
This paper presents the results from a pilot field study that was performed by the ORD in
association with the NADCA. The field study was conducted in nine residential dwellings and
was intended to improve our understanding of the effectiveness of ADC and its impact on
residential IAQ and system performance.
AIR DUCT CLEANING RESEARCH
To better understand the effectiveness and impact of ADC, the EPA conducted a pilot
field study in association with the NADCA. The study was conducted in nine residential
dwellings. Eight of the residences were occupied and the ninth was the EPA's IAQ Test House in
Cary, NC.
Objectives
The objectives of the pilot field study were to:
1. Collect information on the effectiveness of currently available ADC methods used on
residential HAC systems,
2. Collect information on the impact of ADC on the IAQ in residences,
3. Collect information on the impact of cleaning on the system performance,
4. Collect information that can be used to guide future research into ADC.
Approach
In order to meet these objectives, a field study was conducted in nine residences in the
Raleigh, Durham, and Chapel Hill area of North Carolina. The field study was completed during
the summer of 1996. Each of the nine participating houses in the study had a central (whole-
house) HAC forced air distribution system, ADC had not been performed for at least 10 years,
and smoking was not permitted. The goal was to obtain study houses with a variety of duct
material types and configurations.
A week-long study was performed at each house, with all ADC activities and equipment
provided by the NADCA. NADCA used the most current cleaning technologies, procedures, and
state-of-the-art equipment. Table 1 indicates the activities during the week-long study at each of
the nine houses. Table 2 summarizes the characteristics of each of the study houses.
Sampling techniques
Sampling procedures and instrumentation were identical for each of the test houses and
are discussed below. The critical measurements and parameters included supply and return air
2
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duct deposition rates, airborne particle mass (PM) measurements including PM2 5 and PM10,
airborne fiber mass measurements, bacteria and fungi measurements, environmental indicators
including temperature, relative humidity, and carbon dioxide (C02), and system performance
factors such as static pressure, air flow rates, motor current, and refrigerant temperature.
1. Duct deposition sampling The levels of dust in ducts (g/m2) were determined by
collection of dust samples at selected locations using two methods: a Medium Volume Deposition
Sampler (MVDS) method developed for this field study and the NADCA Standard Method 1992-
01 "Mechanical Cleaning of Non-Porous Air Conveyance System Components" (NADCA 1992).
Both methods use gravimetric measurements to determine deposition.
2. Particle sampling Particle mass in the size range of 2.5 fim (PM2 5) and 10 /xm
(PM10) was measured at three locations at each house: outdoors, generally in the area of the
backyard, and at two locations indoors. One location was in a high traffic area such as the front
room or living room. The other was in a low traffic area such as a second bedroom.
Measurements were taken using the size selective impactors developed by Harvard University.
This measurement technique is currently being used in two of EPA's building studies: the Large
Buildings Study and the Building Assessment Survey Evaluation Program. The impactors collect
particle matter in the less than 10 //m diameter and less than 2.5 fj,m diameter size fractions on
Teflon filters. The samples are collected using pumps that operate at 20 L/min, which provides
sufficient mass over a 24 hour sampling period for accurate and precise weighing with a
microbalance.
Additional particle sampling (number/m3) was performed using Climets (model CI-4100)
throughout the test period at each house. The monitor was used in the >0.5 fj.m particle size
mode so that all particles greater than that size are counted. The real-time measurements of
particle number concentrations were augmented by use of a LAS-X particle size/counter. The
instrument was collocated with the Climet to measure room concentrations. The LAS-X was used
to measure concentrations in the size fraction of approximately 0.1 to 3 fim geometric diameter.
3. Fiber monitoring Fiber concentrations were monitored continuously using a MIE
FAM-1 Fibrous Aerosol Monitor. The instrument operates on the light scattering principle. Also,
integrated samples of airborne fibers were collected using the NIOSH Method 7400, Asbestos and
Other Fibers by PCM. Samples were collected on 25 mm cellulose ester membrane filters (0.8
fim pore diameter) housed in a conductive cowl. A nominal sample volume of 2800 L was
collected over a 24-hour period. Total fiber concentrations were determined in accordance with
NIOSH Method 7400B counting rules. Additionally, one filter collected prior to ADC and one
collected after ADC were analyzed by scanning electron microscope (SEM) to determine the
relative abundance of different types of fibers, such as fiber glass, cellulose fibers, and hair.
4. Microbiological measurements The microbiological sampling effort included
bioaerosol measurements and microbial density (filter and swab) determinations. Initially, each
house was inspected to identify areas of particular interest. These would include locations that had
obviously been saturated with water, areas with visible microbial contamination, visible return air
duct leaks into a crawl space, and odors.
Bioaerosols were measured before and 24-36 hours after ADC in the ducts and in the
house using a Mattson-Garvin bioaerosol sampler. Microbial areal density filter and swab
measurements included dust sample collection from a known area of the duct surface by either
3
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vacuuming it onto a filter or wiping the area with a wet swab. The measurements consisted of a
determination of the predominant viable culturable genus of microorganisms collected and the
microbial populations at that particular sampling location before and after ADC.
5. Environmental measurements Temperature, relative humidity, and C02
concentrations were monitored continuously in the primary living area of each house using the an
IAQ data logging system developed by the EPA.
ADC Methods
The ADC methods and equipment employed by NADCA varied according to the house air
distribution system, configuration, and accessibility. Generally, the following procedures were
used:
1. Two types of portable negative air systems were used to collect and remove loosened
dust, dirt, and debris. A high efficiency filtered system was used indoors and a non-filtered system
was used outdoors. Truck mounted vacuum units were not used on this project.
2. Dust, dirt, and debris were loosened from the HAC system and ductwork using silica-
carbide rotating brushes, air washing with compressed air and air whips, contact vacuuming, and
hand wiping.
3. All registers and diffusers were removed and wet-cleaned using a non-toxic cleaning
fluid.
4. The air handler was substantially disassembled and cleaned using hand wiping and
contact vacuuming.
5. The air handling unit fan, impeller, and housing scroll were removed and wet-cleaned
using a non-toxic cleaning fluid. Condensate drain pan, piping, and pump were inspected and
cleaned as necessary. A substantial effort was expended in cleaning the air handling unit.
6. System filters were removed and cleaned or replaced.
7. System cooling coils were wet-cleaned in place using a non-toxic cleaner. Heating
coils were wiped and hand vacuumed.
8. NADCA routinely performed a high level of visual inspections during the cleaning to
ensure that the ADC process was proceeding satisfactorily.
9. Access to the ductwork was generally through end-caps. Access doors were installed
in the ductwork when access to work areas was difficult.
10. The amount of time and labor for NADCA to perform the ADC was fairly consistent.
Generally, two workmen would require 8 to 10 hours to clean a house. Three workmen could
perform the work in an 8 hour period.
Results
1. NADCA ADC methods and techniques were very effective in removing deposition from
ductwork surfaces. The pre-cleaning deposits ranged from an average of 1.5 to 26.0 g/m2. Post-
cleaning deposition ranged from 0.06 to 1.97 g/m2 with an average of 0.43 g/m2 for all samples.
Table 3 shows the results of all deposition sampling.
2. Measurements using the NADCA 1992-01 Standard ranged from 1.0 to 36.0 g/m2 (0.01
to 0.36 mg/100 cm2), meeting the NADCA criterion that residual dust must be less than 1.0
mg/100 cm2 to demonstrate that ADC was effective. Comparing these findings to the MVDS
showed that the collection efficiency of the MVDS was higher than the NADCA method. The
results suggest that the NADCA criterion should be higher, perhaps 5 mg/100 cm2 if the MVDS is
4
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used for evaluating post-cleaning effectiveness.
3. Indoor respirable (PM2 5) and inhalable (PM10) particle mass concentrations were low at
the houses, ranging from 4.2 to 32:7 //g/m3, consistent with results from past studies in houses
without tobacco smoking. PM measurements indoors and outdoors suggest that, during this
study, the indoor concentrations were strongly impacted by outdoor concentrations. The
indoor/outdoor ratios for the integrated particle samples were less than 1.0 for all but 2 of 72 sets
of samples collected. The post-cleaning/pre-cleaning ratios measured indoors were greater than
1.0 at seven of the nine houses; however, at all but one of these seven houses, the post-
cleaning/pre-cleaning ratio was also greater than 1.0 for the outdoor respirable concentrations.
The inhalable particle mass concentrations indoors and outdoors followed similar, but less clear,
trends. These findings suggest that, even though ADC is very effective in removing ductwork
deposition, a potential source of particulate matter (PM), the before and after indoor airborne
concentrations were not substantially different. This is probably because of the strong effect of the
outdoor PM concentrations and other sources, such as occupant activities, cooking, and pets.
Table 4 shows the results of PM measurements.
4. Measurements of indoor particle concentrations (particles/m3) did not show substantial
differences in airborne particle concentrations before and after ADC. The mean concentrations of
particles in a >0.5 //m size fraction measured indoors following ADC were lower only at the EPA
Test House and at two of the eight occupied houses. The post-cleaning/pre-cleaning ratio was
near 1.0 at two houses, but higher than 1.0 at the other four occupied houses. Measurement
results at two houses that were cleaned on the same week and located across the street from each
other suggest that the outdoor particle levels had a strong impact on indoor particle
concentrations. At both houses, indoor particle concentrations increased on Sunday and Monday
following cleaning, even though the houses were cleaned on different days, the HAC system
operation patterns differed, and occupant activities differed dramatically at the two houses. The
occupants of House 4 were not at home most of the Saturday through Monday time period.
5. The impact of ADC without the use of biocides on the levels of bacteria in samples
collected from the surfaces of the HAC system was highly variable. Pre-cleaning bacteria levels
ranged from 5 to 1100 cfu/cm2 in the supply ducts and from 5 to 2300 cfii/cm2 in the return ducts,
with a mean of less than 200 cfu/cm2 in most houses. Mean concentrations of return air bacteria
levels were lower after ADC in six of seven houses; however, in the supply ducts, this was true
for only four of the occupied houses. Pre-cleaning versus post-cleaning differences were
generally small.
6. Fungal levels were generally higher than bacteria levels. ADC had the most impact on
the ducts with the highest levels of fungi and noticeably reduced the level of fungi in samples
collected from ductwork in most houses. Table 5 shows sample findings from supply and return
ductwork.
7. Measurements of HAC system performance factors suggest that ADC had a positive
impact. Because of the small sample size (only nine study houses) and the limited duration of the
measurements, it is not possible to quantitatively determine the significance of ADC on system
performance and energy use. ADC generally resulted in increased air flow to the house. Supply air
flows increased between 4 to 32% at eight houses based on measurements at the floor registers
and diffiisers in the house. Some of the increase in supply air flow rates may have been
5
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attributable to minor repairs of leaks in the ducts and at loose floor boots of supply registers.
Return air flows measured at the return air grilles increased 14 to 38% at two houses, but were
not substantially different after ADC at the other seven houses.
8. Air handling unit (AHU) blower motor current increased after ADC at the four field
study houses where the measurements were performed. Static pressure increased in the return air
ductwork at the six houses with complete measurements. The increase in blower motor current
and increase in static pressure in the return air ducts suggest improved system performance. There
was no clear trend for changes in static pressure in the supply ducts or the differential pressures
across the cooling coil. Refrigerant line surface temperatures did not provide useful information.
Conclusions
1. The results of the nine house pilot field study have demonstrated that ADC methods
and equipment commonly used by HVAC cleaning contractors for source removal are effective in
removing particulate and fibrous contamination in the HAC, thus removing one potential source
of particle and fiber mass in the study houses.
2. The impact of ADC on levels of bacteria and fungi on surfaces of ductwork could not
be fully evaluated because chemical biocides were not used in this study.
3. The MVDS sampling method developed for this study was shown to be appropriate for
quantitatively assessing the effectiveness of the ADC procedures used in the study.
4. Results of measurements of HAC system-related parameters indicate a positive impact
on HAC system performance, although the impact could not be quantified in this study due to the
small study population (nine houses) and the short monitoring period.
5. The short-term air monitoring, sampling methods, and protocols were not adequate for
assessing the impact of ADC on airborne particle and fiber concentrations.
6. Due to the multiple sources of air contaminants in the houses and temporal variability in
airborne concentrations, differences in these IAQ parameters could not be determined between the
pre-cleaning and post-cleaning periods.
7. Results of this pilot study indicate the need for further research on HVAC cleaning in a
number of areas. Additional research, using alternative methods, would help to quantitatively
determine the impact of ADC on IAQ parameters. Research would also help to quantify the
impact of ADC on energy use for residential HAC systems.
8. Additional areas of possible research include: evaluation of methods for cleaning porous
duct materials, the use of biocides during cleaning, effectiveness and durability of encapsulants
applied to porous duct materials, and methods for reducing contamination in HVAC systems.
6
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Table 1. Typical field study house activities
Activity
Day
Microbial
sampling*
PM sampling
indoors and
outdoors6
Deposition
sampling'
NADCA
cleaning
Fiber
sampling"1
Environ. &
system
sampling'
Saturday
~
~
~
~
/
Sunday
/
~
~
Monday
~
/
~
Tuesday
~
Wednesday
/
/
~
/
/
Thursday
/
/
/
Friday
/
~
~
a. Pre- and post-cleaning duct surface sampling for fungi and bacteria
b. Pre- and post-cleaning PM2.5 and PM10 sampling
c. Pre- and post-cleaning duct deposition sampling
d. Pre- and post-cleaning airborne fiber sampling
e. Pre- and post-cleaning environmental measurements using a datalogging system
Table 2. Characteristics of field study test houses
No.
House
Age
(yrs)
Duct
Age
(yrs)
Air
Handler
Age
(yrs)
Duct
Material
House
Size
(ft7m2)
No. of
Floors
No. of
Adults
No. of
Children
Pets
EPA
Test
House
20
20
20
Galv w/
FGDL
& Flex*
1305/121.2
1
0
0
0
2
22
22
22
Galv1"
1520/141.2
1
2
2
1 cat
3
18
18
0.5
Galv&
Flexc
1450/134.7
1
2
0
0
4
10
10
10
Flexd
1980/183.9
2
2
2
0
5
9
9
9
Flex"
2000/185.8
2
2
2
0
6
28
not
avail.
not
avail.
Galv"
1955/181.6
1.5
2
2
1 cat
7
25
25
not
avail.
Galv&
Flexc
1000/92.9
1.5
3
0
2 dogs
2 cats
8
26
26
26
Galv"
2000/185.8
2
2
2
0
9
35
35
not
avail.
Galv1
1500/139.3
2
2
2
1 cat
a. Galvanized sheetmetal ducts with internal fiberglass ductliner insulation and insulated flexible branch ducts
b. Galvanized sheetmetal ducts with external fiberglass wrap insulation
c. Galvanized sheetmetal ducts with external fiberglass wrap insulation and insulated flexible branch ducts
d. Insulated flexible ducts
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Table 3. Dust levels measured in the HAC systems of the study houses.
House No.
Summary
Duct Dust Mass (g/m2)
Statistic
Supply
Return
Air Handler*
Pre-
Post-
Pre-
Post-
Pre-
Post-
EPA
Mean
2.33
0.74
_b
_b
NS
NS
Test
Std. Dev.
1.61
0.37
-
-
House
Min
0.8
0.27
-
-
Max
4.66
1.24
-
-
Number of samples
6
6
-
"
2
Mean
8.62
0.30
19.83
0.58
1.7
NS
Std. Dev.
10.6
0.09
6.60
0.06
2.35c
0.29'
Min
0.51
0.24
26.3
0.54
Max
26.3
0.41
13.1
0.63
Number of samples
5
5
3
2
3
Mean
3.37
0.21
24.13
0.44
NS
0.18C
Std. Dev.
2.09
0.08
23.52
0.23
Min
2.12
0.16
7.50
0.28
Max
5.79
0.30
40.80
0.60
Number of samples
3
3
2
2
4
Mean
1.91
0.25
7.80
0.28
1.57
0.19
Std. Dev.
1.05
0.09
5.30
0.12
0.72c
_d
Min
0.54
0.16
2.62
0.19
Max
3.00
0.35
13.15
0.42
Number of samples
4
3
3
3
5
Mean
1.48
0.27
7.89
0.12
0.46
0.10
Std. Dev.
0.29
0.11
2.35
0.08
1.81c
0.12"
Min
1.27
0.19
6.22
0.06
Max
1.69
0.34
9.55
0.17
Number of samples
2
2
2
2
6
Mean
2.28
0.59
11.34
1.11
2.24
0.13
Std. Dev.
0.48
0.39
0.21
1.22
Min
1.94
0.32
11.19
0.25
Max
2.62
0.87
11.49
1.97
Number of samples
2
2
2
2
7
Mean
2.30
0.18
5.26
0.15
2.24°
0.13c
Std. Dev.
0.26
0.00
1.69
0.04
Min
2.00
0.18
3.62
0.12
Max
2.45
0.18
6.99
0.19
Number of samples
3
2
3
3
8
Mean
3.34
0.50
12.91
0.32
6.18
0.25
Std. Dev.
1.79
0.17
5.48
0.03
2.38°
_d
Min
1.24
0.37
9.03
0.30
Max
5.93
0.69
16.78
0.34
Number of samples
6
3
2
2
9
Mean
26.03
0.79
35.11
0.39
5.48c
_d
Std. Dev.
8.41
0.35
13.85
0.28
Min
16.39
0.44
26.59
0.19
Max
36.07
1.13
51.10
0.59
Number of samples
4
3
3
2
a. Single samples were collected from the foil liner or cooling coil
b. Return air duct replaced; no samples collected
c. Cooling coil samples
d. Cooling coil could not be sampled post-cleaning because it was wet
NS: No sample collected due to logistical or access problems
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TABLE 4. ADC impact on airborne PM? 5 and PMin concentrations
House
Location'
PM
PM10
Mg/m3
^g/m3
Pre-Cleaningb
Post-Cleaningb
Ratio of
Post/Pre
Pre-Cleaningb
Post-Cleaningb
Ratio of
Post/Pre
EPA
Test
House
Outdoor
23.3
20.4
0.88
28.1
26.1
0.93
Primary
7.5
10.3
1.37
11.1
29.0
2.61
Secondary
7.8
10.8
1.38
9.5
14.2
1.49
2
Outdoor
8.6
28.1
3.27
14.4
33.8
2.35
Primary
6.5
15.3
2.36
10.7
22.1
2.07
Secondary
6.3
16.0
2.54
8.6
18.7
2.17
. 3
Outdoor
11.6
29.3
2.53
18.7
32.8
1.75
Primary
11.8
16.9
1.43
15.2
19.2
1.26
Secondary
10.5
16.8
1.60
12.1
13.1
1.08
4
Outdoor
35.0
25.3
0.72
42.1
28.5
0.68
Primary
16.5
13.3
0.80
17.7
17.4
0.98
Secondary
16.7
12.3
0.74
18.9
16.2
0.86
5
Outdoor
24.6
33.8
1.37
28.8
41.5
1.44
Primary
11.8
25.7
2.17
15.6
33.6
2.15
Secondary
10.8
21.9
2.03
12.6
11.0
0.87
6
Outdoor
14.4
22.8 .
1.59
19.0
30.3
1.59
Primary
5.7
10.3
1.81
10.0
13.6
1.36
Secondary
5.2
10.7
2.05
8.7
13.8
1.59
7
Outdoor
14.8
21.6
1.46
23.4
20.6
0.88
Primary
6.5
6.8
1.05
10.3
9.7
0.94
Secondary
8.3
8.3
1.01
9.7
8.4
0.87
8
Outdoor
21.3
12.5
0.59
26.2
21.0
0.80
Primary
11.7
8.5
0.73
14.3
11.4
0.79
Secondary
11.3
7.7
0.68
13.2
11.3
0.86
9
Outdoor
13.7
17.4
1.27
26.2
22.1
0.84
Primary
11.3
13.2
1.17
10.9
12.7
1.17
Secondary
7.7
10.9
1.42
15.7
13.7
0.87
a. Measurements were performed at an outdoor location and in two rooms in the home, generally a family room (primary) and a secondary lesser used
room
b. Mean for 2 days prior to and 2 days following ADC
9
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TABLE 5. Surface samples of fungi in supply and return ducts
House
Summary
Statistic
Cfu/cm2
Supply Duct
Return Duct
Pre-cleaning
Post-cleaning
Pre-cleaning
Post-cleaning
1
Mean
35,700
1,206
2,650
Ĥa
Max
250,000
4,700
4,800
a
2
Mean
9,217
138
280
153
Max
19,000
640
320
260
3
Mean
4,604
740
22,333
147
Max
8,300
1,700
26,000
190
4
Mean
73,400
15,890
850
617
Max
160,000
36,000
1,200
1,000
5
Mean
35
46
58
71
Max
110
120
90
140
6
Mean
113
61
613
7
Max
110
130
2,600
15
7
Mean
1,089
49
2,200
23
Max
3,900
150
2,400
40
8
Mean
63
7
196
10
Max
170
15
320
15
a. No samples collected
10
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REFERENCES
Ahmed, I., B. Tansel, and J.D. Mitrani. 1994. Effectiveness of HVAC sanitation processes
in improving indoor air quality. Technical publication No. 113. Florida International University,
Miami, FL.
Batterman, S. and H. Burge. 1995. HVAC systems as emission sources affecting indoor
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Proceedings of the 1st Annual EPA/AWMA International Symposium on Engineering Solutions to
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11
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nrmrl-rte-p-195 111 miiiiiiiimil miiiiii ii
1. REPORT , , ^ '2.
EPA/600/A-98/009
3. 11111 llll 1 Mil Ĥ 1
PB98-137433
4. TITLE AND SUBTITLE
Update on EPA's Air Duct Cleaning Research
Activities
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Russell N. Kulp
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING OROANIZATION NAME AND ADDRESS
NA (Inhouse)
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
NA (Inhouse)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper;FY95-FY96
14. SPONSORING AGENCY CODE
EPA/600/13
15. supplementary notes appcd project officer is Russell N. Kulp, Mail Drop 54, 919/
541-7980. For presentation at 5th Annual Indoor Environment '97, Baltimore, MD,
4/7-9/97.
i6.abstractpaper updates a current U.S. EPA, Office of Research and Develop-
ment (ORD) pilot field study, related to simple residential heating and air-condition-
ing (HAC) systems, that was recently conducted in nine houses. Investigations pro- .
vided information on the effectiveness of air duct cleaning (ADC) and its impact on
indoor air quality (IAQ). Pre- and post-cleaning measurements included duct depo-
sition, particle and fiber mass, and microbiological sampling. All ADC activities
and equipment were provided by the National Air Duct Cleaners Association (NAD-
CA). Results indicate that ADC is effective in removing deposition from non-porous
surfaces in HAC systems. Pre-cleaning deposition rates ranged from an average of
1. 5 to 26.0 g/sq m. Post-cleaning deposition ranged from 0.06 to 1.97 g/sq m, with
and average of 0.43 g/sq m for all samples. Measurements of indoor respirable
(PM2. 5) and inhalable (PM10) particle mass were low at the houses, ranging from
4.2 to 32.7 /ug/cu m, consistent with results from past studies in houses without to-
bacco smoking. Pre- and Post-cleaning PM measurements were not substantially
different. Similar results were found for particle concentrations. Bacteria levels
were highly variable. Mean concentrations of bacteria from surfaces of return air
ducts were lower after cleaning in over half of the test houses.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Sampling
Ducts
Ventilation
Cleaning
Particles
Fibers
Pollution Control
Stationary Sources
Indoor Air Quality
Particulate
Microbes
13 B 14 B
13K
13A
13H
14G
he
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
Release to Public SaCaiilbteSopvJ^
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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