Mold and HVAC Air Filters

Indoor Air Quality Professionals

Selecting an air filter for your hvac can be complicated. Improperly maintaining your heating and air-conditioning system may cause serious air quality problems. Please call our professionals to discuss a filter application. Here is some information about air filtration options.


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Summary from the epa research web-site

Three strategies (in order of effectiveness) that may be used to reduce indoor air pollutants are 1) source control, 2) ventilation, and 3) air cleaning. Air cleaning may achieve an additional reduction in the levels of certain pollutants when source control and ventilation do not result in acceptable pollutant concentrations. However, air cleaning alone cannot be expected to adequately remove all of the pollutants present in the typical indoor air environment.

Air cleaners are usually classified by the method employed for removing particles of various sizes from the air. There are three general types of air cleaners on the market: mechanical filters, electronic air cleaners, and ion generators. Hybrid units, using two or more of these removal methods, are also available. Air cleaners may be in-duct units (installed in the central heating and/or air-conditioning system) or stand-alone portable units.

The effectiveness of air cleaners in removing pollutants from the air is a function of both the efficiency of the device itself (e.g., the percentage of the pollutant removed as it goes through the device) and the amount of air handled by the device. A product of these two factors (for a given pollutant) is expressed as the unit's dean air delivery rate (CADR).

Portable air cleaners vary in size and effectiveness in pollutant reduction capabilities. They range from relatively ineffective table-top units to larger, more powerful console units. In general, units containing either electrostatic precipitators, negative ion generators, or pleated filters, and hybrid units containing combinations of these mechanisms, are more effective than flat filter units in removing tobacco smoke particles. Effectiveness within these classes varies widely, however. For removal of larger dust particles, negative ion generators, without additional particle capture mechanisms (e.g., filters), may perform poorly.

Pollutants in indoor air may be divided, for convenience, into three groups: particles, gaseous pollutants, and radon and its progeny. Some air cleaners, under the right conditions, can effectively remove small particles which are suspended in air. However, controversy exists as to the efficacy of air cleaners in removing larger particles such as pollen and house dust allergens, which rapidly settle from indoor air. In assessing the potential efficacy of an air cleaner in removing allergens, one should consider the relative contribution of airborne to surface concentrations of the allergens, particularly in the case of pollen and house dust allergens where natural settling may be so rapid that air cleaners contribute little additional effect. Animal dander may settle more slowly although, again, the surface reservoir far exceeds the amount in the air. Furthermore, control of the sources of allergens and, where allergens do not originate outdoors, ventilation should be stressed as the primary means of reducing allergic reactions

Some of the air cleaners containing sorbents may also remove some of the gaseous pollutants in indoor air. However, no air-cleaning systems are expected to totally eliminate all hazards from gaseous pollutants and these systems may have a limited lifetime before replacement is necessary. In addition, air cleaning may not be effective in reducing the risks of lung cancer due to radon.

In choosing an air cleaner, several factors should be considered. These include:

 The potential effectiveness of the device under the conditions it will be used.

 The need for routine maintenance, including cleaning and replacement of filters and sorbents.

 The estimated capital and maintenance cost.

 The installation requirements (e.g., power, access).

 The manufacturer's recommended operating procedures.

The possible production or redispersal of pollutants, such as ozone, particles, formaldehyde, and trapped gaseous pollutants.

 The inability of air cleaners designed for particle removal to control gases and some odors, such as those from tobacco smoke.

 Possible health effects from charged particles produced by ion generators.

 Possible soiling of surfaces by charged particles produced by ion generators.

 The noise level at the air flow rates that will be used.

Finally, one Federal standard, addressing only high efficiency air filters, and two standards provided by independent standard-setting trade associations outside the Federal government may be useful as guidelines in choosing an air cleaner for reduction of particles in indoor air. For induct systems, the atmospheric dust spot test of ASHRAE Standard 52-76 and the DOP method in Military Standard 282 may be used, respectively, to estimate the performance of medium and high efficiency air cleaners. For portable air cleaning systems, ANSI/AHAM AC-1-1988 may be useful in estimating the effectiveness of the units. Similar standards are not currently available to compare the performance of air cleaners in removing gaseous pollutants or radon and its progeny.


1. ASHRAE. 1976. ASHRAE standard 5276. Method of testing air-cleaning devices used in general ventilation for removing particulate matter. New York, NY: American Society of Heating, Refrigerating, and Air-conditioning Engineers Inc.

2. ASHRAE. 1979. Air cleaners. In: ASHRAE handbook and product directory. 1979 equipment. Atlanta, GA: American Society of Heating, Refrigerating, and Air-conditioning Engineers, Inc. As cited in reference 16.

3. U.S. DOD. 1956. MILSTD282. Military Standard. Filter units, protective clothing, gasmask components and related products: Performance test methods. Washington, DC: U.S. Department of Defense.

4. Institute of Environmental Sciences. 1986. Recommended practice for HEPA filters. IES RP-CC-001-86. Mt. Prospect, IL: Institute of Environmental Sciences.

5. Ensor DS, Viner AS, Hanley JT, Lawless PA, Ramanathan K, Owen MK, Yamamoto T, Sparks LE. 1988. Air cleaner technologies for indoor air pollution. In: Engineering solutions to indoor air problems. Proceedings of the ASHRAE conference IAQ'88, April 11-13, 1988, Atlanta, GA. Atlanta, GA: American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc. pp.111-129.

6. Repace JL, Seba DB, Lowrey AH, Gregory TW. 1983. Effect of negative ion generators on ambient tobacco smoke. Journal of Clinical Ecology 2(2): 90-94.

7. New Shelter. 1983. A test of small air cleaners. In: Home products report. Emmaus PA Rodale Press.

8. Offermann FJ, Sextro RG, Fisk WJ, Grimsrud DT, Nazaroff WW, Nero AV, Rezvan KL, Yater J. 1985. Control of respirable particles in indoor air with portable air cleaners. Atmospheric Environment 19(11): 1761-1771.

9. Consumers Union. 1985. Air cleaners. Consumer Reports 50(1): 7-11.

10. Canine C. 1986. Clearing the air. Rodale's New Shelter, January 1986, p. 64-67.

11. Olander L, Johansson J, Johansson R. 1987. Air cleaners for tobacco smoke. In: Seifert B, et al., eds. Indoor air '87. Proceedings of the 4th Conference on Indoor Air Quality and Climate, West Berlin, August 17-21, 1987. Vol. 2. Berlin: Institute for Water, Soil and Air Hygiene. pp. 39-43.

12. Consumers Union. 1989. Air purifiers. Consumer Reports, February 1989, p. 88-93.

13. Humphreys MP. 1987. Performance testing of residential indoor air cleaning devices. Presented at the 1987 EPA/APCA Symposium on Measurement of Toxic and Related Air Pollutants, Research Triangle Park, NC, May 3-6, 1987.

14. Luczynska CM, Li Y, Chapman MD, Platts-Mills TAE. 1988. Airborne concentrations and particle size distribution of allergen derived from domestic cats (Felis domesticus): Measurements using cascade impactor, liquid impinger and a two site monoclonal antibody assay for Fel d I. Presented to the American Academy of Allergy Meeting, Los Angeles, March 4, 1988.

15. National Academy of Sciences. 1981. Indoor pollutants. Washington, DC: National Academy Press.

16. Wadden RA, Scheff PA. 1983. Indoor air pollution. New York: John Wiley and Sons.

17. Electric Power Research Institute. 1984. Manual on indoor air quality. Prepared by Lawrence Berkeley Laboratory, Berkeley, CA for the Energy Management and Utilization Division, Electric Power Research Institute, Palo Alto, CA. EPRI EM-3469.

18. Ramanathan K, Debler VL, Kosusko M, Sparks LE. 1988. Evaluation of control strategies for volatile organic compounds in indoor air. Environmental Progress 7(4): 230-235.

19. Mahajan BM. 1989. A method for measuring the effectiveness of gaseous contaminant removal filters. Gaithersburg, MD. National Institute of Standards and Technology, U.S. Department of Commerce. NBSIR 89-4119.

20. Fisk WJ, Spencer RK, Grimsrud DT, Offermann FJ, Pedersen B, Sextro R. 1987. Indoor air quality control techniques. Radon, formaldehyde, combustion products. Park Ridge, NJ: Noyes Data Corporation.

21. Daisey JM, Hodgson AT. 1989. Initial efficiencies of air cleaners for the removal of nitrogen dioxide and volatile organic compounds. Atmospheric Environment 23(9): 1885-1892.

22. U.S. Environmental Protection Agency. 1989. Radon reduction methods. A homeowner's guide (Third edition). Washington, DC: Office of Research and Development, U.S. Environmental Protection Agency.

23. Nelson HS, Hirsch SR, Ohman JL, PlattsMills TAE, Reed CE, Solomon WR. 1988. Recommendations for the use of residential air-cleaning devices in the treatment of allergic respiratory diseases. Journal of Allergy and Clinical Immunology 82(4): 661-669.

24. Rajala M, Janka K, Graeffe G, Kulmala V. 1984. Laboratory measurements of the influence of air treatment devices on radon daughters. In: Berglund B, Lindvall T, Sundell J, eds. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Stockholm, August 20-24, 1984. Vol. 5. Stockholm: Swedish Council for Building Research. pp. 117-122.

25. Association of Home Appliance Manufacturers. 1988. American national standard method for measuring performance of portable household electric cord-connected room air cleaners. ANSI/AHAM AC-1-1988. Chicago, IL: Association of Home Appliance Manufacturers.

26. Association of Home Appliance Manufacturers. 1989. Comparing room air cleaners. An AHAM buying guide. Chicago, IL: Association of Home Appliance Manufacturers.

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