The Great Debate on How Often HVAC Ducts Should Be Cleaned

Q: I recently purchased my first house, and my real estate agent suggested that I have the heating and air ducts cleaned to remove any dust and hair from the system. Is this really necessary? If duct cleaning is important, how often should I have it done?

A: Your home’s HVAC system carries warm or cool air from the furnace or air conditioner throughout the house via metal ducts. While dirt, dust, hair, and other debris can collect on the insides of these ducts, this does not mean that you have to have the ducts cleaned regularly. Small amounts of debris don’t affect the air quality inside the home, and HVAC ducts don’t need frequent cleaning. However, there are times when cleaning is necessary, including when there is visible mold, an infestation, or excessive dust and dirt blowing out of the vents.

A light amount of household dust, dirt, and debris does not pose a risk to your health.

A common claim by some HVAC companies is that the HVAC ducts in a house should be cleaned at least once every three to five years to ensure that hair, dust, and debris will not affect the air quality in the home and lead to health problems. The EPA takes a different stance, however, noting that duct cleaning has not been shown to prevent health problems. Additionally, studies into the effects of duct cleaning do not conclusively demonstrate that the presence of dust and debris in the ducts will increase the particle levels inside the home.

With this in mind, there is no reason to think that a light amount of household dust, dirt, and debris in the ducts would cause harm to people within the home. In fact, regularly cleaning the ducts may actually stir up dust, increasing particle levels inside the house beyond what they would have been if you had just lived with the lightly soiled ducts.

Consider having the ducts cleaned if there is visible mold growth inside the HVAC system.

While duct cleaning isn’t necessary for a light amount of dust, hair, and other debris, there are certain times when having the ducts cleaned is the best course of action. HVAC ducts carry hot and cold air from the furnace and air conditioner to the rest of the home. The varying temperatures inside and outside the ducts can lead to moisture accumulation within the vents, creating an ideal environment for mold and mildew growth.

Mold and mildew can detrimentally impact your health, so if there is visible mold growth inside the HVAC system, then it’s time to call an HVAC company to have the vents cleaned before the mold and mildew spores can spread to the rest of the home.

Attend to the ducts ASAP if they are infested with rodents or insects.

An accumulation of moisture inside the HVAC system doesn’t just make a great environment for mold and mildew, it’s also attractive to rodents and insects that can use the interconnected ducts to spread quickly throughout the home. Some of these pests, such as mice and rats, can cause significant problems to the infrastructure of the home, while others, including cockroaches, ants, fleas, and bedbugs, can annoy—and in some cases can carry diseases that infect—humans.

Any sign of rodents or insects in the HVAC system is an indication that the ducts need to be professionally cleaned. You may also want to consider hiring an exterminator to ensure that the infestation is completely eliminated from the home.

The ducts need to be cleaned if there is an excessive amount of dust and debris released into the home through the registers.

As already noted, dirt, dust, and hair regularly pass through the HVAC system and can become stuck to the sides of the ducts. In small amounts, this debris doesn’t cause any harm and there is no evidence to suggest that it impacts the quality of the air within the home. In large quantities, however, dust and debris can create an air quality hazard, so it’s important to check the vents regularly and have the ducts cleaned if an excessive amount of debris is being blown into the home through the outlet vents. Additionally, consider having the ducts cleaned if there is a musty, burning smell when the furnace is turned on.

In general, have the ducts cleaned when necessary, but frequent duct cleaning is not needed. 

Most HVAC companies will state a specific frequency or schedule for cleaning the ducts, but regular HVAC cleaning isn’t necessary to maintain the health and air quality of the home. Air quality inside the home isn’t adversely affected by the air blowing through lightly soiled ducts. Just be sure to have the ducts cleaned when there is visible mold, signs of pests, or excessive dust and debris blowing into the rooms.

That said, individuals with sensitive respiratory systems or serious allergies should consider having the ducts cleaned more frequently to reduce dust and dirt buildup before it becomes excessive. It should also be noted that sharing your home with pets that shed will increase the amount of dust, dirt, and hair inside the vents, requiring the ducts to be cleaned more frequently.