Air Duct Cleaning: What’s it all about?

Most people are now aware that indoor air pollution is an issue of growing concern and increased visibility.  Many companies are marketing products and services intended to improve the quality of your indoor air.  You have probably seen an advertisement, received a coupon in the mail, or been approached directly by a company offering to clean your air ducts as a means of improving your home’s indoor air quality. These services typically—but not always—range in cost from $450 to $1,000 per heating and cooling system, depending on the services offered, the size of the system to be cleaned, system accessibility, climatic region, and level of contamination.

If not properly installed, maintained, and operated these components may become contaminated with particles of dust, pollen or other debris.  If moisture is present, the potential for microbiological growth (e.g., mold) is increased and spores from such growth may be released into the home’s living space.  Some of these contaminants may cause allergic reactions or other symptoms in people If they are exposed to them.  If you decide to have your heating and cooling system cleaned, it is important to make sure the service provider agrees to clean all components of the system and is qualified to do so.  Failure to clean a component of a contaminated system can result in re-contamination of the entire system, thus negating any potential benefits.  Methods of duct cleaning vary, although standards have been established by industry associations concerned with air duct cleaning.  Typically, a service provider will use specialized tools to dislodge dirt and other debris in ducts then vacuum them out with a high powered vacuum cleaner.

In addition, the service provider may propose applying chemical biocides, designed to kill microbiological contaminants, to the inside of the duct work and to other system components.  Some other service providers may also suggest applying chemical treatments (sealants or other encapsulants) to encapsulate or cover the inside surfaces of the air ducts and equipment housings because they believe it will control mold growth or prevent the release of dirt particles or fibers from ducts.  These practices have yet to be fully researched and you should be fully informed before deciding to permit the use of biocides or chemical treatments in your air ducts.  They should only be applied, if at all, after the system has been properly cleaned of all visible dust and debris.

Note: Use of sealants to encapsulate the inside surfaces of ducts is a different practice than sealing duct air leaks.  Sealing duct air leaks can help save energy on heating an cooling bills.

Deciding Whether or Not to Have Your Air Ducts Cleaned

Knowledge about the potential benefits and possible problems of air duct cleaning is limited.  Since conditions in every home are different, it is impossible to generalize about whether or not air duct cleaning in your home would be beneficial.

It is normal for the return registers to get dusty as dust laden air is pulled through the grate.  This does not indicate that your air ducts are contaminated with heavy deposits of dust or debris; the registers can be easily vacuumed or removed and cleaned.

On the other hand, if family members are experiencing unusual or unexplained illnesses or sickness, many physicians are now recommending cleaning your air ducts, which may provide relief, especially if they are suffering from allergies or asthma.

You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should occasionally be cleaned.  While the debate about the value of periodic duct cleaning continues, no evidence suggests that such cleaning would be detrimental, provided that it’s done properly.

On the other hand, if a service provider fails to follow proper duct cleaning procedures, duct cleaning can cause indoor air problems.  For example, an inadequate vacuum collection system can release more dust, dirt, and other contaminants than if you left the ducts alone.  A careless or inadequately trained serviced provider can damage your ducts or heating and cooling system, possibly increasing your heating and air conditioning costs or forcing you to undertake difficult and costly repairs or replacements.

You should consider having air ducts cleaned if:

  • Ducts are infested with vermin (rodents,  insects, etc.)
  • Ducts are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers.
  • Ducts or other  heating/cooling system components have substantial visible mold growth on the inside hard surface of sheet metal.

There are several important points to understand concerning mold detection in heating and cooling systems:

  1. Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.
  2. You should be aware that although a substance may look like mold, a  positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.
  3. If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.
  4. If the conditions causing the mold growth in the first place are not corrected, mold growth will recur.

Suggestions for Choosing a Duct Cleaning Service Provider

To find companies that provide duct cleaning services, check your Yellow Pages under “duct cleaning” or contact the National Air Duct Cleaners Association (NADCA) at the address and phone number in the information section located at the end of this guidance.  Do not assume that all duct cleaning service providers are equally knowledgeable and responsible.  Talk to at least three different service providers and get written estimates before deciding whether to have your ducts cleaned.

Contact your county or city office of consumer affairs or local Better Business Bureau to determine if complaints have been lodged against any of the companies you are considering.

Interview potential service providers to ensure:

  • They are experienced in duct cleaning and have worked on systems like yours;
  • They will use procedures to protect you, your pets, and your home from contamination; and
  • They comply with NADCA’s air duct cleaning standards and, if your ducts are constructed of fiber glass duct board or insulated internally with fiberglass, they use equipment that will not damage any internal duct linings.

What to Expect From an Air Duct Cleaning Service Provider

If you choose to have your ducts cleaned, the service provider should:

  • Open access ports or doors to allow the entire system to be cleaned and inspected.
  • Inspect the system before cleaning to be sure that there are no asbestos-containing materials (e.g., insulation, register boots, etc.) in the heating and cooling system. Asbestos-containing materials require specialized procedures and should not be disturbed or removed expect by specially trained and equipped contractors.
  • Use vacuum equipment that exhausts particles outside of the home or use only high efficiency particle air (HEPA) vacuuming equipment if the vacuum exhausts inside the home.
  • Protect carpet during cleaning in inclement weather.
  • Take care to protect the duct work, including sealing and re-insulating any access holes the service provider may have made or used so they are airtight.
  • Follow NADCA’s standards for air duct cleaning and NADCA’s recommended practice for ducts containing fiber glass lining or constructed of fiber glass duct board.   

How to Determine if the Duct Cleaner Did A Thorough Job

A thorough visual inspection is the best way to verify the cleanliness of your heating and cooling system.  All portions of the system should be visibly clean; you should not be able to detect any debris with the naked eye.