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.
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 dust or 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. In addition, following this post-cleaning check list can help to ensure a top quality job.
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 inspect your system and 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.
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:
• Smokers in the household.
• Pets that shed high amounts of hair and dander.
• Water contamination or damage to the home or HVAC system.
• Residents with allergies or asthma who might benefit from a reduction in the amount of indoor air pollutants in the home’s HVAC system.
• After home renovations or remodeling.
• Prior to occupancy of a new home.
The most effective way to clean air ducts and ventilation systems is to employ Source Removal methods of cleaning. This requires a contractor to place the system under negative pressure, through the use of a specialized, powerful vacuum. While the vacuum draws air through the system, devices are inserted into the ducts to dislodge any debris that might be stuck to interior surfaces. The debris can then travel down the ducts to the vacuum, which removes it from the system and the home.
Antimicrobial chemicals are applied by some companies to the interior surface of the air ducts, to treat microbial contamination such as fungi (mold), viruses or bacteria. Before any antimicrobial chemicals are used, the system should be thoroughly cleaned. It is critical that any antimicrobial treatment used in your system be registered by the U.S. Environmental Protection Agency specifically for use in HVAC systems. The use of antimicrobial chemicals is an additional service that is not part of a typical air duct cleaning project.
You should interview as many local contractors as possible. Ask them to come to your home and perform a system inspection and give you a quotation. To narrow down your pool of potential contractors, use the following pre-qualifications:
• Make sure the company is a member in good standing of the National Air Duct Cleaners Association (NADCA).
• See if the company has been in business long enough to have adequate experience.
• Get proof that the company is properly licensed and adequately insured.
• Verify that the company is certified by NADCA to perform HVAC system cleaning.
• Make sure that the company is going to clean and visually inspect all of the air ducts and related system components.
• Avoid advertisements for "$99 whole house specials" and other sales gimmicks.
• Ask if the company has the right equipment to effectively perform cleaning, and if the company has done work in homes similar to yours. Get references from neighbors if possible.
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 beware of air duct cleaning companies that making sweeping claims about the health benefits of duct cleaning – such claims are unsubstantiated. 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.)
NADCA does not endorse one kind of equipment over another. 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 NADCA standards.
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 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.”)
NADCA Members have signed a Code of Ethics stating they will do everything possible to protect the consumer, and follow NADCA Standards for cleaning to the best of their ability, for a list of NADCA members near you, click here. Air duct cleaning companies must meet stringent requirements to become a NADCA Member. Among those requirements, all NADCA Members must have certified Air System Cleaning Specialists (ASCS) on staff, who have taken and passed the NADCA Certification Examination. Passing the exam demonstrates extensive knowledge in HVAC design and cleaning methodologies. ASCSs are also required to further their industry education by attending seminars in order to maintain their NADCA certification status.
You may view the NADCA Code of Ethics here.
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.