As awareness of the importance of indoor air quality grows, more people are looking at duct cleaning as one way to solve indoor air quality problems. Air duct cleaning is the physical cleaning of heating, ventilating, and air-conditioning (HVAC) system components including ducts, air terminals (supply and return), heat exchangers (heating and cooling coils), condensate drains and pans, fan motors and housings, system filters, and the air handling unit housing. However, little published data exist on the impact of air duct cleaning on residential indoor air quality or energy costs (Kulp, et al.).
Individuals who are considering having their ducts cleaned should first determine that contaminated ducts are the cause of their health problems. Even when contaminants are present in ducts, the source may lie elsewhere, so cleaning ducts may not permanently solve the problem.
HVAC air supply ducts are typically a sealed system. However, they can be a potential source of dust and related microbial contamination. The type of duct work, the way the ducts are sealed, the filtration system and external contaminants affect the condition of the ductwork. “A major biopollutant reservoir and source is internal, acoustical man-made insulation or duct liner, installed for noise control. Dust and debris that circulates in the HVAC system can, over time, accumulate on the insulating material. Then, when sufficient moisture becomes available through water leaking into the ductwork or from condensation of water vapor due to temperature changes from day time to night time, fungal and bacterial spores germinate, amplify, and disseminate through the system and into the occupied spaces” (Cole, 1999). The combination of dust and moisture invariably leads to microbial growth, often in ductwork in the absence of internal insulation.
The key to preventing air duct relation pollution problems is a combination of proper design and dedicated inspection and maintenance. Eliminating the source for the pollutants is much more cost effective than cleanup or replacement.
Internal porous insulation should be precluded from use in ductwork. Ducts can be insulated externally using fiberglass wrap. If internal porous insulation is determined to be a source of microbial contamination, then it must be removed or the ductwork replaced, as opposed to the use of antimicrobials, biocides, sealants, or encapsulants.
If you suspect that the ducts are the problem, call a reputable HVAC company for an inspection. They should do a thorough inspection and give a report of conditions with a proposed cleaning plan. If it is determined that you need to have the ducts cleaned, discuss with the service provider how they are going to perform the job. Will the service provider take steps to protect individuals from exposure to dislodged pollutants and chemicals used during the cleaning process? Will a HEPA filtration vacuum be used when cleaning? How will the service provider assure that contaminants will not be exhausted back into the house? Will workers wear respirators for their protection? Will household occupants vacate during cleaning? What type of guarantee do they provide?
- “Air Cleaning Devices and Duct Cleaning,” American Lung Association. http://www.lungusa.org/air/cleaning_factsheet99.html.
- “A Pilot Study to Evaluate the Impact of Air Duct Cleaning on Indoor Air Quality in Residences,” Russell N. Kulp, National Risk Management Research Laboratory, et. al. Research Triangle Park, NC.
- “HVAC Ducts in Schools: Pollutant Sources Through Poor Design,” Eugene C. Cole, DrPH, Durham, NC.
- National Air Duct Cleaners Association. http://wwwnadca.com/.
Prepared by Janie L. Harris, M.Ed., CRS, former Extension Housing and Environment Specialist, Texas A&M AgriLife Extension Service, Texas A&M System. 2000.
Last updated: July 2, 2015