Are there any health benefits that come from HVAC system cleaning?

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.

How can we determine if the HVAC system cleaning was effective?

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.

How long should it take to clean a typical residential HVAC system?

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.

How often should residential HVAC systems be cleaned?

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.
How should a residential HVAC be cleaned?
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.
What are antimicrobial chemicals and why would they need to be used?

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.

What criteria should I use when selecting an HVAC system cleaner?

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.
What is the normal price range for the air duct cleaning service?

The Environmental Protection Agency says that “duct cleaning services typically – but not always – range in cost from $450 up 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 provincial elected officials to demand legislation.)

What kind of equipment is best for cleaning truck mounted vacuums or portable vacuums?

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.”)

Why should I choose a NADCA member to have my air ducts cleaned?

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.

Will HVAC system cleaning reduce our home energy bills?

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.

Is it ok to have an exterior vent screen on my dryer duct?


The following is an example of one major dryer manufacturer’s “typical recommendations”

(Excerpt re-printed from MAYTAG Web Site in the public domain)

  • Read the manufacturer’s installation instructions.
  • If at all possible, use 4-inch diameter rigid aluminum or rigid galvanized steel duct.
  • Do not use smaller duct.
  • If flexible metal duct must be used, use the type with a stiff sheet metal wall.
  • Do not use flexible duct with a thin foil wall.
  • Never use plastic flexible duct.
  • Do not exhaust the dryer into any wall, ceiling, crawl space or a concealed space of a building, gas vent or any other common duct or chimney.
  • Keep exhaust duct as straight and short as possible.
  • Exhaust systems longer than the manufacturer’s recommendations can extend drying times, affect appliance operation and may collect lint.
  • These recommendations may vary somewhat for various dryer brands and should be checked when installing the dryer.
    The exhaust hood on the outside of the house should have a swing out damper to prevent back drafts and entry of wildlife.
  • Never use an exhaust hood with a magnetic damper.
  • The hood should have at least 12 inches of clearance between the bottom of the hood and the ground or other obstruction.
  • The hood opening should point down.
  • Never install a screen over the exhaust outlet.

End of excerpt

Other additional general information re “exterior dryer vent – screens”

  • In a perfect world “exterior dryer vents should not be fitted with vent screens”.
  • Note: we often find “exterior dryer vents fitted with mesh vent screens” that are “blocked on the inside / backside of the vent screens” with “thick blanket / layers of dryer lint” (and blocked screens eventually choke & block the dryer ducts)
  • We strongly recommend that exterior dryer vent screens be permanently removed to prevent dryer lint build-up on the vent screens and, to allow the dryer ducts to vent safely and efficiently (without any restriction) out to atmosphere.
  • Note: dryer lint “will be produced during every normal drying cycle” and “dryer lint particles will enter the dryer duct”.
  • Note: if exterior dryer vent screens are to remain in place and dryer lint particles become trapped on the exterior dryer vent screens”; *this is not the fault of our professional dryer duct cleaning work*.

Note: for general information purposes the following “paragraph excerpt” has been reproduced (from the public domain)



504.4 Exhaust Installation:

  • Dryer exhaust ducts for clothes dryers shall terminate on the outside of the building and shall be equipped with a back-draft damper.
  • Screens shall not be installed at the duct termination.
  • Ducts shall not be connected or installed with sheet metal screws or other fasteners that will obstruct the exhaust flow.
  • Clothes dryer exhaust ducts shall not be connected to a vent connector, vent or chimney.
  • Clothes dryer exhaust ducts shall not extend into or through ducts or plenums.
I live in a concrete building in a condo and my ceiling is wet and leaking from the dryer duct and my clothes are taking longer to dry
  • We see your situation every day and, we strongly recommend cleaning all “in-slab dryer ducts” in concrete buildings “from inside and from outside”.
  • Because: typically in concrete buildings the dryer duct exhaust system is configured as follows:
  • The “dryer unit” vents through “a 4″ round diameter flex pipe” which then connects to “a narrow duct transition elbow” situated in the ceiling cavity and;
  • The transition elbow “changes shape from a 4″ round diameter duct” to a “narrow rectangular duct shape” to join the “long – main in-slab dryer duct”.
  • The long “main in-slab dryer duct” is “narrow and rectangular shaped” and runs horizontally in the concrete ceiling slab.
  • The long “main in-slab dryer duct” then vents (out to atmosphere) through a rectangular “fin style – exterior dryer vent” (at the balcony or wall face).
  • In addition (because the dryer ducts in concrete buildings are often “long and narrowduct runs”) “dryer duct – booster fans” are often installed by builders to “boost and improve dryer duct air-flow”.
  • Note: to clean in-slab dryer duct systems correctly;
  • The “narrow – transition elbows” should be cleaned from inside (because; the “narrow transition elbows” are often found “blocked with hardened (“cement like”) solid plugs of dryer lint”) and:
  • The “dryer duct – booster fans” should be “inspected, tested and cleaned” (to verify the fans are working and to keep the “fan paddle blades & fan casing – inner walls” free from lint build-up and, help prolong “fan motor life” and, to help to prevent “condensation, moisture & water pooling” in long dryer ducts).
  • The “exterior dryer ducts & exterior dryer vents & vent screens” should be cleaned from outside (because the “vents & screens” are often found “blocked on the inside of the vents” with “thick blanket / layers of dryer lint”) and:
  • Note: in a perfect world, exterior “dryer vents should not be fitted with screens“.
  • We often find “exterior dryer vents fitted “with narrow gapped fins or mesh screens” that are “completely blocked on the inside / backside of the vent screens” with “thick blanket / layers of dryer lint” (and the blocked screens eventually choke and block the dryer ducts).
  • We strongly recommend that “exterior dryer vent screens” be replaced with “exterior dryer vents – fitted with back draft dampers” to prevent dryer lint build-up on the screens and, to allow the dryer ducts to vent safely and efficiently (and unrestricted) out to atmosphere.
  • Note: dryer lint “will be produced during every normal drying cycle” and, “dryer lint particles will enter the dryer ducts” and if dryer vent screens remain in place, the dryer lint will become trapped on the exterior dryer vent screens”.

How can I keep my Dryer Duct System working safely and efficiently?
Please call MASDUCT and we will help and provide information guidelines to assist you.

(Content on this page has been sourced from NADCA www.nadca.com)