EPA/600/A-98/Q26 EVALUATING RESIDENTIAL AIR DUCT CLEANING AND IAQ: RESULTS OF A FIELD STUDY CONDUCTED IN NINE SINGLE ' FAMILY DWELLINGS Russell Kulp1, Roy Fortmatin2, Gary Gentry2, Douglas VanOsdeli3, Karin Foarde3, Tim Hebert4, Robert Krell4, and Charlie Cochrane4 1 U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA 2 Acurex Environmental Corporation, Research Triangle Park, North Carolina, USA 3 Research Triangle Institute, Research Triangle Park, North Carolina, USA 4 National Air Duct Cleaners Association, Washington, District of Columbia, USA ABSTRACT A nine-home field study was conducted to investigate the impact of mechanical air duct cleaning (ADC) methods on indoor air quality (IAQ) and system performance. ADC services were provided by the National Air Duct Cleaners Association (NADCA). Only mechanical ADC methods were evaluated. Surface treatments, such as biocides or encapsulants, were not part of the study, Pre- and post-ADC measurements were used to evaluate impacts. These included deposited duct dust measurements, airborne particle and fiber concentrations, microbial bioaerosol and surface sampling, and system performance factors such as temperature, relative humidity, air flow rates, and static pressure. Surface sampling in ducts indicated that mechanical ADC is effective in removing adhered dust and dirt. The particle measurement data could not offer a clear indication that indoor levels can be reduced using mechanical ADC because there was an apparent strong influence from outdoor particle mass concentrations. Mechanical ADC did not significantly reduce bioaerosol or microbial density in the houses studied. Measurements of system performance factors suggest that ADC may have a positive effect. Supply air rates increased between 4 and 32% in eight of the houses and return air flow rates increased 14 and 38% in two of the houses. INTRODUCTION The U.S. Environmental Protection Agency (EPA), Office of Research and Development (ORD) and NADCA are actively engaged in research that is designed to focus on issues related to IAQ, source management., and their relationship to the ADC industry (1). This paper presents the results of a field study performed by the EPA and NADCA. Nine residences were studied with the intention of improving our understanding of residential ADC procedures. The objectives were to evaluate mechanical ADC methods commonly used to clean non-porous surfaces and to measure pre- and post-ADC environmental system parameters to investigate any impacts on IAQ and system performance. Surface treatments such as biocides and encapsulants were not a part of the field study. METHODS The study was conducted in nine residential dwellings. Eight of the residences were occupied. The ninth was the EPA's IAQ Test House (TH) in Gary, NC. Each house was equipped with a I ------- central heating and air-conditioning (HAC) forced air distribution system. ADC had not been performed on the AHU (air handling unit) or duct system for at least 10 years, and all occupants were nonsmokers. Table 1 shows the house characteristics. These houses presented NADCA with a variety of system configurations for ADC. A week-long study was carried out at each house. The Acurex Environmental Corporation and the Research Triangle Institute performed all environmental and system measurements. Table1. Characteristics of field study test houses No. 1 2 3 4 5 6 7 8 9 House Age (yrs) 20 22 18 10 9 28 25 26 35 Duct Age (yrs) 20 22 18 10 9 not avail. 25 26 35 AHU Age (yrs) 20 22 0.5 10 9 not avail. not avail. 26 not avail. Duct Material a b c d d b c b b House Size (m2) 121.2 141.2 134.7 183.9 185.8 181.6 92.9 185.8 139.3 No. of Floors 1 1 1 2 2 1.5 1.5 2 2 a. Galvanized sheet-metal trunk ducts with internal fiberglass ductliner insulation and insulated flexible plastic branch ducts b. Galvanized sheet-metal ducts with external fiberglass wrap insulation c. Galvanized sheet-metal trunk ducts with external fiberglass wrap insulation and insulated flexible plastic branch ducts d. Insulated flexible ducts Sampling procedures and instrumentation were identical for each of the test houses. Pre- and post-ADC measurements included supply and return air duct dust surface mass, airborne particle mass (PM) and fiber measurements, microbiological measurements, temperature, relative humidity, and carbon dioxide (CO2), and system performance factors such as static pressure, air flow rates, motor current, and refrigerant temperature. Levels of dust in the ducts (grams per square meter) were determined by collection of deposited dust samples at selected locations using two methods, the Medium Volume Deposition Sampler (MVDS) (2) and the NADCA Standard Method 1992-01 (3); The MVDS was developed for this study so that both pre- and post-cleaning deposition dust levels could be evaluated. The current NADCA Standard Method 1992-01 can be used to evaluate only post-cleaning levels. PM ranges of 2.5 fj,m (PM2 5) and 10 /^m (PM10) were measured at three locations, outdoors and at two indoor locations. Measurements were taken using the size selective impactors developed for use in the EPA's Building Assessment Survey Evaluation (BASE) Program (4). ------- Additional particle sampling (particles per cubic meter) was performed using a Climet model CI-4100. The monitor was used in the >0.5 /zm particle size mode so that all particles greater than that size were counted. These real-time measurements of particle number concentrations were augmented by use of a LAS-X particle size/counter. The LAS-X was collocated with the Climet and was used to measure room concentrations in the size fraction of approximately 0.1 to 3 /mi geometric diameters. Fiber concentrations were monitored continuously using a MIE FAM-1 Fibrous Aerosol Monitor. Also, integrated samples of airborne fibers were collected using the NIOSH Method 7400, Asbestos and Other Fibers by PCM (5). Total fiber concentrations were determined in accordance with NIOSH Method 740GB counting rules. Additionally, a filter sample 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. Bioaerosol samples were taken in the ducts and in the houses using either a Mattson-Garvin slit-to-agar sampler or a 1-stage Andersen cascade sampler. Microbial surface density measurements were conducted near where the duct dust deposition samples were taken using filter cassette and sterile swab techniques. Temperature, relative humidity, and CO2 concentrations were monitored continuously in the primary living area of each house using the IAQ data logging system developed by the EPA. The mechanical ADC methods and equipment employed by NADCA varied according to the house air distribution system, configuration, and accessibility. ADC methods included portable negative air systems to collect and remove loosened dust and debris. Silica-carbide rotating brushes, air washing with compressed air and air whips, contact vacuuming, and hand-wiping were used to loosen the dust and debris. A substantial effort was expended in cleaning the AHU. It was substantially disassembled and cleaned using hand-wiping and contact vacuuming. The fan, impeller, and scroll housing were removed and wet-cleaned using a non-toxic cleaning fluid. The condensate drain pan, piping, and pumps were inspected and cleaned as necessary. System filters were removed and cleaned or replaced. System cooling coils were wet-cleaned in place using a non-toxic cleaner. Heating coils were wiped and hand vacuumed. NADCA routinely performed a high level of visual inspections during the cleaning to ensure that the ADC process was proceeding satisfactorily. Access to the ductwork was generally through end caps and flexible duct connections. Access doors were installed in the ductwork when access to work areas was difficult. Registers and difiusers were removed and wet- cleaned using a non-toxic cleaning fluid. RESULTS The mechanical ADC methods employed appeared to be effective in removing deposited dust from duct surfaces. Figure 1 shows pre- and post-cleaning measurements in the supply ducts at ------- all of the test houses using the MVDS. Pre-cleaning supply duct deposition ranged from 1.48 g/m2 at house no. 5 to 26.03 g/m2 at house no. 9. Figure 1 shows that post-cleaning supply duct measurements ranged from 0.18 g/m2 at house no. 7 to 0,79 g/m2 at house no. 9. These measurements do not meet the NADCA criterion that residual dust must be less than 0.1 g/m2 (3). o Q. ju - 75 - "?n . i*i - m „ 0 - I m 1 | | TH sa— • s % 1^_ |L 1 23456 House number ESSH** m I 7 J?!|_ 8 M n t '%. 1 1 •M 4, P 1 S_ 9 m Pre-clean Post-clean Figure 1. Supply duet deposition measurements using MVDS On the other hand, post-cleaning supply duct measurements using the NADCA Standard Method, which are not shown,' ranged from 0.003 g/m2 at house no. 8 to 0.036 g/m2 at house no. 2. These measurements meet the NADCA criterion for residual dust (3). Baseline 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 studies in houses without tobacco smoking (6). Interpretation of the PM measurement data is difficult because outdoor concentrations will have an impact on indoor concentrations. The outdoor concentrations varied over the course of each week-long study making it difficult to determine if the changes in indoor concentrations after ADC were the result of cleaning or due to changes in either outdoor concentrations or occupant activities. For the same reasons, the Climet data were inconclusive with respect to determining ADC impact. Again, these data suggest that the outdoor PM concentrations may have such a strong influence on indoor levels that airborne particle differentials from pre- to post-ADC cannot be detected. A comparison of average pre- and post-ADC bioaerosol levels shows a reduction in airborne fungi; however, these reductions are not considered substantial. None of the test houses were considered to be biocontaminated; therefore, a small change would not be surprising. Pre-ADC airborne fungi levels in the supply ducts ranged from 14 to 646 cfij/m3 while the post-ADC ------- levels ranged from 2 to 300 efu/m3, > Bacteria in samples collected from the surfaces of the HAC system were highly variable; Pre- ADC bacteria levels ranged from 5 to 1100 cfli/cm2 in the supply ducts and from 5 to 2300 cfu/cm2 in the return ducts, with a mean for all samples of less than 200 cfu/em2. 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- versus post-ADC differences were generally small. Fungal levels were generally higher than bacteria levels, and ADC had the most impact on the ducts with the highest levels of fungi and noticeably reduced the level of fungi in surface samples collected from ducts in most houses. Measurements of system performance factors suggest that ADC had a positive impact. Because of the small sample size and the limited duration of the measurements, it is not possible to quantitatively determine the significance of ADC on system performance and energy use. Generally it resulted in increased air flow to the house. Supply air flows increased between 4 and 32% at eight houses based on measurements at the floor registers and diffusers in the house. Part of the increase in supply air flow rates may have been attributable to minor duct repair. 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. AHU blower mot or'current increased after ADC at the four field study houses where the measurements were performed. Static pressure increased in the return air duct at the six houses with complete measurements. The increases in both blower motor current and 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. DISCUSSION Heating, ventilating, and air-conditioning (HVAC) systems contaminated with adhered dirt and dust deposition are potential IAQ emission sources (7). Research shows that HVAC total volatile organic compound emission rates and odors may be effectively reduced by removing deposition (8)(9)(10). This field study demonstrated that mechanical ADC methods can be an effective source management tool when applied to non-porous bare sheet-metal ducts. Porous surfaces, such as fibrous glass duct lining (FGDL), were not evaluated because houses with FGDL systems, but without visible surface mierobial contamination, could not be found. When FGDL becomes microbiaOy contaminated, the EPA and N1OSH recommend removal and replacement rather than any form of ADC (i 1). Further research is required to evaluate ADC effectiveness on porous surfaces. Differentials in indoor PM levels from pre- to post-ADC could not be detected. This is consistent with previous research (12) and is probably due to the strong influence of outdoor PM sources (6). Mechanical ADC methods alone did not substantially reduce bioaerosol and culturable surface ------- microbial levels. Surface treatments such as biocides or encapsulates may be required if it is determined that substantial reductions are necessary. To folly evaluate this, future research should include comparisons using mechanical ADC in combination with surface treatments. The MVDS sampling method appeared to be an effective way to quantitatively assess both pre- and post-cleaning duct deposition levels. The MVDS was specially designed for this study and has a higher collection efficiency than the NADCA Standard Method due to the higher air flow rate and use of a brush on the nozzle (3). The data from this study demonstrate that the NADCA Standard 1992-01 criterion of 0.1 g/m2 to document the effectiveness of cleaning should be applied only to samples collected with the Standard 1992-01 method. The criterion of 0.1 g/m2 is not appropriate for samples collected with the MVDS sampling method. Results from other EPA research (13) suggest that a criterion of approximately 0,5 g/m2 may be more appropriate for samples collected with the MVDS. Results of measurements of HAC system-related parameters suggest that there is a positive impact on HAC system performance from mechanical ADC. These measured impacts cannot be considered significant due to the small study population and the short monitoring period. To substantiate these findings, further research is required. REFERENCES 1. Kulp, R.N. EPA begins air duct cleaning research, Inside IAQ, EP A's Indoor Air Quality Research Update. EPA/60Q/N-95/004, Spring/Summer 1995, pp. 10-11. Environmental Protection Agency, Research Triangle Park, NC 27711; 1995. 2. Kulp, R.N. Update on EPA 's Air Duct Cleaning Research Activities. Proceedings of Indoor Environment '97. IAQ Publications, Chevy Chase, MD 20815; 1997; pp. 24-34. 3. NADCA. Mechanical cleaning of non-porous air conveyance system components: standard 1992-01. National Air Duct Cleaners Association. Washington, DC 20005; 1992. 4, Womble, S.E., J.R. Girman, and R. Highsmith. EPA BASE Program: collecting baseline information on indoor air quality. Proceedings of IAQ'94: Engineering Indoor Environments. American Society of Heating, Refrigerating and Air- Conditioning Engineers, Inc. Atlanta, GA 30329; 1994. 5. NIOSH. Method 7400 - asbestos and other fibers by PCM. NIQSH Manual of Analytical Methods. Fourth Edition. National Institute for Occupational Safety and Health, Cincinnati, OH 45268; 1994. 6. Wallace, L. Indoor particles: a review. Journal of the Air & Waste Management Association, Pittsburgh, PA 15222; 1996. 46:98-126. 7. Batterman, S. and H. Surge. HVAC systems as emission sources affecting indoor air quality: a critical review. Report No. EPA-600/R-95-014 (NTIS PB95-178596). Environmental Protection Agency. Research Triangle Park, NC 27711; February 1995. ------- 8, Ishikawa, K., T. Iwata, H. Ito, K. Kumagai, K. Kumura, and S. Yoshizawa. Field investigation on the effectiveness of duct cleaning on indoor air quality with measured results of WOC and perceived, air quality. Proceedings of Indoor Air '96, the 7* International Conference on Indoor Air Quality and Climate, 1996. Vol. 2, pp. 809- 814. 9. Fanger, P.O. et al. Air pollution source in office and assembly halls, quantified by the olfunit. Energy and Buildings. 1988. Pp. 1-6. 10. AIVC. Duct cleaning - a literature survey. Air Infiltration Review, vol. 14, No. 4, Air Infiltration and Ventilation Centre, Coventry, UK; 1993. 11. EPA, Building air quality: a guide for building owners and facility managers. EPA- 400/1-91-033 (GPO 055-000-00390-4). U.S. Environmental Protection Agency. Washington, DC 20460. National Institute for Occupational Safety and Health. Washington, DC 20468. 1991. 12. Fugler, D. and M: Auger. A first look at the effectiveness of residential duct cleaning. Proceedings of the 87* Annual Meeting & Exhibition. Air & Waste Management Association. Pittsburgh, PA 15222; 1994. 13. Van Osdell, D.W., Foarde, K.K., Fortmann, R.C., and Kulp, R.N. Pilot Air Conveyance System Design, Characterization, and Cleaning. Proceedings of Engineering Solutions to Indoor Air Quality Problems. Air & Waste Management Association. Pittsburgh, PA 15222; 1997. ------- NRMRL-RTP-P-249 TECHNICAL REPORT DATA (Please read faftruetions on the reverse before con 2. , TITLE AND SUBTITLE Evaluating Residential Air Duct Cleaning and LAQ: Results of a Field Study Conducted in Nine Single Family Dwellings 5. REPORT DATE 6, PERFORMING ORGANIZATION CODE AUTHORS E.Kulp (EPA); R. Fortmann and C. Gentry (Acurex); D. VanOsdell and K.Foarde (RTI); and T.Hebert. R.Krell. and C. Cochrane (NADCA) 8, PERFORMING ORGANIZATION REPORT NO. . PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO. A curex Environmental Corp., RTF, NC Research Triangle Institute, RTF, NC National Air Duct Cleaners Assn, Washington, DC 11. CONTRACT/GRANT NO. 68-D4-0005 (Acurex), CR82 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 COVf Published paper; FY95-9( RED 14. SPONSORING AGENCY CODE EPA/6QO/13 is. SUPPLEMENTARY NOTES 541-7980. Presented at CD project officer is Russell M. Kulp. IAQ '97, Washington, DC, 9/27-10 /2T/97. Mail Drop 54, 919 / IB. ABSTRACT paper gj_ves results of a nine-home field study of the impact of mechan- ical air duct cleaning (ADC) methods on indoor air quality (IAQ) and system perfor- mance. ADC services were provided by the National Air Duct Cleaners Association (NADCA). Only mechanical ADC methods were evaluated. Surface treatments, such as biocides or encapsulants, were not part of the study. Pre- and post-ADC measure ments were used to evaluate the impacts. These included deposited duct dust mea- surements, airborne particle and fiber concentrations, microbial bioaerosol and surface sampling, and system performance factors such as temperature, relative humidity, air flow rates, and static pressure. Surface sampling in ducts indicated that mechanical ADC is effective in removing adhered dust and dirt. The particle measurement data could not offer a clear indication that indoor levels can be reduced using mechanical ADC because there was an apparent strong influence from outdoor particle mass concentrations. Mechanical ADC did not significantly reduce bioaero- sol or microbial density in the houses studied. Measurements of system performance factors suggest that ADC may have a positive effect. Supply air rates increased be- tween 4 and 32% in eight of the houses, and return air flow rates increased between 14 and 38% in two of the houses. 17. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.lDENTIFlERS/OPEN ENDED TERMS c. COSATI Field/Group Pollution Particles Residential Buildings Ducts Fibers Ventilation Aerosols Cleaning Dust Pollution Control Stationary Sources Indoor Air Quality (IAQ) P articulate Bioaerosols 13B 13 M 13K ISA 13H 11G 14G HE 07D 18. DISTRIBUTION STATEMENT Release to Public 19. SECURITY CLASS (This Report) Unclassified 21. NO. OF PAGES 20. SECURITY CLASS (This page) Unclassified 22. PRICE EPA Form 2220-1 19-73) ------- |