HVAC Air Duct Cleaning: Necessary or Not?

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.

Unlike dryer duct cleaning which should be regularly checked and cleaned, no independent objective organization recommends HVAC duct cleaning as an essential part of routine HVAC system maintenance.
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.