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
- level of contamination
If you decide to have your heating and cooling system cleaned, it important to make sure the service provider agrees to clean all components of the system and is qualified to do so.
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.
If no one in your household suffers from allergies or unexplained symptoms or illnesses and if, after a visual inspection of the inside of the ducts, you see no indication that your air ducts are contaminated with large deposits of dust or mold (no musty odor or visible mold growth), having your air ducts cleaned is probably unnecessary. 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 symptoms or illnesses that you think might be related to your home environment, you should discuss the situation with your doctor. EPA has published the following publications for guidance on identifying possible indoor air quality problems and ways to prevent or fix them.
- Indoor Air Quality: An Introduction for Health Professionals
- The Inside Story: A Guide to Indoor Air Quality
You should consider having the air ducts in your home cleaned if:
- There is substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system.
- Ducts are infested with vermin, e.g. (rodents or insects)
- Ducts are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers.
How to Prevent Duct Contamination
Whether or not you decide to have the air ducts in your home cleaned, committing to a good preventive maintenance program is essential to minimize duct contamination.
To prevent dirt from entering the system:
- Use the highest efficiency air filter recommended by the manufacturer of your heating and cooling system.
- Change filters regularly.
- If your filters become clogged, change them more frequently.
- Be sure you do not have any missing filters and that air cannot bypass filters through gaps around the filter holder.
- When having your heating and cooling system maintained or checked for other reasons, be sure to ask the service provider to clean cooling coils and drain pans.
- During construction or renovation work that produces dust in your home, seal off supply and return registers and do not operate the heating and cooling system until after cleaning up the dust.
- If your heating system includes in-duct humidification equipment, be sure to operate and maintain the humidifier strictly as recommended by the manufacturer.
Whether of not you decide to have the air ducts in your home cleaned, committing to a good preventive maintenance program is essential to minimize duct contamination.
To prevent ducts from becoming wet:
Moisture should not be present in ducts. Controlling moisture is the most effective way to prevent biological growth in air ducts.
Unresolved Issues of Duct Cleaning
Does duct cleaning prevent health problems?
The bottom line is: no one knows. There are examples of ducts that have become badly contaminated with a variety of materials that may pose risks to your health. The duct system can serve as a means to distribute these contaminants throughout a home. In these cases, duct cleaning may make sense. However, a light amount of household dust in your air ducts is normal. Duct cleaning is not considered to be a necessary part of yearly maintenance of your heating and cooling system, which consists of regular cleaning of drain pans and heating and cooling coils, regular filter changes and yearly inspections of heating equipment. Research continues in an effort to evaluate the potential benefits of air duct cleaning.
In the meantime
- Educate yourself about duct cleaning by contacting some or all of the sources of information listed at the end of this publication and asking questions of potential service providers.
Are duct materials other than bare sheet metal ducts more likely to be contaminated with mold and other biological contaminants?
You may be familiar with air ducts that are constructed of sheet metal. However, many modern residential air duct systems are constructed of fiber glass duct board or sheet metal ducts that are lined on the inside with fiber glass duct liner. Since the early 1970’s, a significant increase in the use of flexible duct, which generally is internally lined with plastic or some other type of material, has occurred.
The use of insulated duct material has increased due:
- to improved temperature control
- energy conservation
- reduced condensation
In the meantime
Experts do agree that moisture should not be present in ducts and if moisture and dirt are present, the potential exists for biological contaminants to grow and be distributed throughout the home. Controlling moisture is the most effective way to prevent biological growth in all types of air ducts.
- Correct any water leaks or standing water.
- Remove standing water under cooling coils of air handling units by making sure that drain pans slope toward the drain.
- If humidifiers are used, they must be properly maintained.
- Air handling units should be constructed so that maintenance personnel have easy, direct access to heat exchange components and drain pans for proper cleaning and maintenance.
- Steam cleaning and other methods involving moisture should not be used on any kind of duct work.
Should chemical biocides be applied to the inside of air ducts?
Air duct cleaning service providers may tell you that they need to apply a chemical biocide to the inside of your ducts to kill bacteria (germs) and fungi (mold), and prevent future biological growth. Some duct cleaning service providers may propose to introduce ozone to kill biological contaminants. Ozone is a highly reactive gas that is regulated in the outside air as a lung irritant. However, there remains considerable controversy over the necessity and wisdom of introducing chemical biocides or ozone into the duct work.
No products are currently registered by EPA as biocides for use on fiberglass duct board or fiberglass lined ducts so it is important to determine if sections of your system contain these materials before permitting the application of any biocide.
In the meantime
Before allowing a service provider to use a chemical biocide in your duct work, the service provider should:
- Demonstrate visible evidence of microbial growth in your duct work. Some service providers may attempt to convince you that your air ducts are contaminated by demonstrating that the microorganisms found in your home grow on a settling plate (i.e., petri dish). This is inappropriate. Some microorganisms are always present in the air, and some growth on a settling plate is normal. As noted earlier, only an expert can positively identify a substance as biological growth and lab analysis may be required for final confirmation. Other testing methods are not reliable.
- Explain why biological growth cannot be removed by physical means, such as brushing, and further growth prevented by controlling moisture.
- Show you the biocide label, which will describe its range of approved uses.
- Always use the product strictly according to its label instructions.
