Heating, ventilation, and air conditioning (HVAC) systems have been shown to act as a collection source for a variety of contaminants that have the potential to affect health, such as mold, fungi, bacteria, and very small particles of dust. The removal of such contaminants from the HVAC system and home should be considered as one component in an overall plan to improve indoor air quality.

Research by the U.S. EPA has demonstrated that HVAC system cleaning may allow systems to run more efficiently by removing debris from sensitive mechanical components. Clean, efficient systems are less likely to break down, have a longer life span, and generally operate more effectively than dirty systems.

There are two main types of vacuum collection devices: (1) those mounted on trucks and trailers, and (2) portable units. Truck/trailer mounted equipment is generally more powerful than portable equipment. However, portable equipment can often be brought directly into a facility, allowing the vacuum source to be located closer to the ductwork. Both types of equipment will clean to standards. Large, more powerful equipment is highly desired because noise and debris is outside your home or office. All vacuum units should be attached to a collection device for safe containment prior to disposal. Any vacuum collection device which exhausts indoors must be HEPA (high efficiency particulate air) filtered. A vacuum collection device alone will not get an HVAC system clean. The use of methods and tools designed to agitate debris adhered to the surfaces within the system, in conjunction with the use of the vacuum collection device(s), is required to clean HVAC systems. (For example: brushes, air whips, and “skipper balls.”) Vacuum collection device hose sizes vary. Obviously an 8" diameter hose can handle significantly larger pieces of debris then a 2" diameter hose. Therefore, one may want to ask a potential contractor about their hose size.

Frequency of cleaning depends on several factors, not the least of which is the preference of the home owner. Some of the things that may lead a home owner to consider more frequent cleaning include:

• Residents with allergies, asthma, emphysema (COPD) or other respiratory conditions who might benefit from a reduction in the amount of indoor air pollutants in the home’s HVAC system.
• Smokers in the household.
• Pets that shed high amounts of hair and dander.
• Water, bacteria, mold or other contamination or damage to the home or HVAC system.
• Following home renovations or remodeling.
• Prior to occupancy of a new home.

The Environmental Protection Agency says that “duct cleaning services typically – but not always – range in cost from $450 to $1000 per heating and cooling system, depending on the services offered, the size of the system to be cleaned, system accessibility, climactic region, and level of contamination” and type of duct material. Consumers should also beware of “blow-and-go” air duct cleaning companies. These companies often charge a nominal fee and do a poor job of cleaning the heating and cooling system. These companies may also persuade the consumer into unneeded services with and/or without their permission. (If you have knowledge of a practicing “blow-and-go” air duct cleaner, contact your local Better Business Bureau to report the company, and your local, federal, and state elected officials to demand legislation.)

Interview as many local contractors as you can. Ask them to give you a price quotation. Talk with them at length about their experience, reputation, process, charges, etc. This simple phone call strategy can tell you a great deal about the business and their staff. To narrow down your pool of potential contractors, use the following pre-qualifications:

• Ask if the company has been in business long enough to have adequate experience.
• Ask for proof that the company is properly licensed and adequately insured.
• Avoid advertisements for "$99 whole house specials" and other sales gimmicks. Read the "fine print"
• Ask if the company has the right equipment to effectively perform cleaning, and if the company has done work in homes similar to yours.
• Ask if they are going to clean and visually inspect all of the air ducts and related system components.
• Ask them to describe their process.
• Ask for references.

Sanitizers are anti-microbial chemicals applied to the interior surface of the air ducts, designed to control microbial contamination. Before any sanitizers are used, the system should be thoroughly cleaned. It is critical that any anti-microbial treatment used in your system be EPA registered for the intended use in HVAC systems. Ask about the specific product to insure they are not substituting alcohol based or "perfume" deodorant water that mask odor but do nothing to eliminate or retard growth. Such substances have the potential of irritating human and animal sensitive respiratory systems.

The amount of time it takes to clean a residential HVAC system depends on many variables such as the size of the home, the number of systems, the extent of the contamination and the number of HVAC cleaners performing the job. Ask at least two contractors to give you a time estimate for your particular system. This will give you a general idea of how long the job should take as well as an idea of how thoroughly the contractor plans to do the job.

The best way to determine if the HVAC system cleaning was effective is to perform a visual inspection of the system before and after cleaning. If any debris can be seen during the visual inspection, the system should not be considered cleaned. While you can perform your own visual inspection using a flash light and mirror, a professional cleaning contractor should be able to allow you better access to system components and perhaps the use of specialized inspection tools.