A popular HVAC "maintenance" item that seems to get a lot of attention is that of duct cleaning. It seems like a logical maintenance activity but cleaning the air ducts in your home’s HVAC system may not be as good an idea as it intuitively seems. Let's explore some of the issues.
- Do ducts get dusty? Yes.
- Is that normal? Yes.
- Should you regularly clean your ductwork? No.
In fact the Environmental Protection Agency states the “EPA does not recommend that air ducts be cleaned except on an as-needed basis because of the continuing uncertainty about the benefits of duct cleaning under most circumstances.”
It also states…“Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space.”
Now I’m not saying duct cleaning is a bad idea, just that it is not necessarily good or even, well, necessary in most cases. In this link I'll show you a picture of the interior of ductwork from my home built in 1937. The duct has never been cleaned. See what you think.
Properly performed, duct cleaning can be useful in limited situations such as if the ducts are filthy or infested with mice or other vermin, or if you see evidence of significant visible mold growth in the ducts or on the mechanical components of the HVAC system that come in contact with air.
But cleaning normally dusty ducts provides no real value.
Frightening “before” and “after” duct photos may make great discount coupon photos but chances are rare that your ducts are in bad shape. If your ducts are seriously filthy enough to require it to be cleaned, then you should clean the entire HVAC system (more on that later), not just the ducts themselves.
Please understand that duct cleaning uses specialized tools to agitate and dislodge dirt in the ducts to make the dirt and other contaminants increasingly loose and airborne before they are vacuumed out. Sometimes the ducts are cut for tool access and needs to be carefully resealed. Then a powerful vacuum system is used to remove the loosened dirt and contaminants. If this is not done properly you can do more harm than good.
For example, if the vacuum hose / containment system is not sealed tightly and exhausting contaminants to the outside, or if a HEPA filtration system is not used in an interior vacuum system, you can wind up releasing dirt and contaminants into your home’s interior. As part of the duct cleaning process, your ducts may have service holes cut into it for tool or vacuum hose access that may not be properly sealed after use, or HVAC system components could be taken apart and damaged or not reinstalled properly, and so on.
So how do you minimize risk? Well, start by selecting and using a qualified contractor. Duct and HVAC system cleaning performed properly and by a NADCA (National Air Duct Cleaning Association) trained and certified operator has the best chance of being done safely.
According to NADCA, the major trade association for contractors doing air duct / HVAC system cleaning, its members need to have at least one certified Air Systems Cleaning Specialist (ASCS) on staff and they are responsible to clean and restore a customer’s HVAC system accordance with the association’s standards and guidelines. Of course NADCA certification is no guarantee of a problem free experience but it does at least improve your chances. I would not have my home’s ducts cleaned without the contractor being NADCA certified.
Duct Cleaning or HVAC System Cleaning
Part of the confusion in discussing duct cleaning services is that duct cleaning is often included as a part of an overall HVAC system cleaning. As a matter of fact, since the only time cleaning your ducts is required is when they are contaminated, it follows that if you need to clean the ducts, then you need to clean the entire HVAC system that comes in contact with the air moving through the ducts.
That is the philosophy taken by NADCA.
NADCA recommends duct cleaning as part of an overall HVAC system cleaning that includes replacing / cleaning the air filter, cleaning grilles and diffusers, checking drain pans and drain lines for proper drainage, checking the heat exchanger and cooling coils, grills, furnace air plenum, blower motor, etc. They provide a useful Checklist for Residential Consumers that explains their recommended process in more detail.
According to NADCA the following items should be covered in a HVAC cleaning service:
- Clean main supply duct and branch distribution ducts;
- Clean return air ducts;
- Seal all installation access panels in ducts (as needed for tool access) according to NADCA standards.
Grills and Diffusers
- Remove and visibly clean supply registers and return air grilles;
- Clean furnace supply air plenum and return air plenum;
- Clean furnace heat exchanger;
- Remove, clean and reinstall blower motor; housing & assembly;
- Check humidifier media and drain pan;
- Clean evaporator coil, drain, and pan drain;
- Ensure cooling coil is visibly clean and drain pan is clean and draining properly;
Furnace Air Filter
- Replace air filter or wash permanent media air filter.
Be prepared to pay around $500 to $1,000.00 for a professional duct / HVAC system cleaning servicing, more or less depending on the location, size of your home and scope of what is cleaned. It will usually take 2 technicians 3 to 5 hours to clean the ducts and the HVAC system.
SCAMS: Beware of the “Blow and Go”
Problems emerge when duct cleaning is not performed properly. And not being performed properly often resulted from hiring someone who promises to give you a cheap $50 “whole house special” or makes a sales pitch based on broad generalized claims on the health benefits of duct cleaning. Some may even falsely claim to be EPA (environmental Protection Agency) certified which the EPA does not provide, or say the EPA recommends duct cleaning which it again does not recommend.
Be aware of what are called “blow-and-go” salesmen / “contractors” who you may find in those mail-pack coupons. They usually accompany an offer to assess or clean your home’s ducts for a very cheap price, say $49.95 or even less. As they often work on commission they will try high pressure sales techniques to sell you on expensive add-on services (mold testing, etc) or other service upgrades or charge for duct restoration, branch duct cleaning, etc. Some may even falsely claim they found mold in your ducts. Complaints abound about some unscrupulous “blow-and-go” companies using air fragrances, false mold tests showing positive results, hand held dust-buster vacuums, using simple drills with brushes, creating air borne dust and not sealing service access holes cut into ductwork.
I know the allure of a low price can be attractive but do the math! You cannot get 2 qualified service technicians with a truck and proper equipment and insurance to go to your home to service your ducts and HVAC system for 4 hours and do this work for $50!
Duct cleaning is an emotional sell. You want good air quality for you and your family and intuitively cleaning the ducts in your home makes sense. Some marketing photos of dirty ducts can look pretty scary. But the reality is that ducts only needs to be cleaned in rare cases, when there is serious contamination in them and then the entire HVAC system should be cleaned, not just the ducts. Cleaning ducts is easy to do wrong and that is where the risk lies. Hiring the wrong contractor can do more harm than good, and falling prey to “$50 Whole House Specials” in those coupon books you receive in the mail is a sure way to invite a bad experience.
Properly performed by a qualified technician, HVAC system cleaning including duct cleaning, has not been shown to be detrimental, but again, that’s if it is done correctly and by a certified technician with the right equipment and training.
At the end of the day, the EPA sums it up by saying “Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts.”