How To Tell If Mold Is Growing In Your Vents

by Grace Motley

In 2001, CBS News ran a story about toxic mold, calling it a "silent killer." Not only does mold devalue homes, it also places the health of a home's inhabitants at risk. People living in close contact with mold can suffer from headaches, congestion, skin and eye irritation and respiratory problems. While mold sometimes grows out in the open where homeowners can easily see it, mold can also grow unseen and undetected in the HVAC system. Knowing how to identify the signs of mold in the ventilation system can save homeowners and their family members from this potentially dangerous problem. 


A common sign of mold growing in the home is the presence of a persistent musty odor in the house. Mold can grow anywhere in the home and the odor will be noticeable whether it's growing in the vents or not. However, if mold is in the HVAC system, the musty odor will be particularly noticeable when the furnace or air conditioner kicks on. As the air circulates around the house, so does the smell.  

Health Response

People living in homes with mold growing in the vents may become sick; and symptoms are likely to worsen when the furnace or air conditioner is running. It's important to note that not all people react to mold in the same way, and some people don't react at all. One, many or all the people in one household may become sick when exposed to mold, and not all symptoms may be the same. The greatest indicator that a home has a mold problem will be the persistence of the illness. As long as a family is living in a house with mold, they are unlikely to recover from the ill effects. 

Visual Confirmation

Mold grows in colonies that look like clusters made up of spots. Mold may be black, orange, brown, white or green. It may be fuzzy and tall or flat. Although a visual confirmation is basically proof that the vents in a home have a mold problem, a lack of visual confirmation is not proof that mold is not present.   

Mold can grow in the vents because of moisture or humidity, or because of leaks and flood damage. To prevent these problems, homeowners must fix all leaks immediately, run the climate controls when humidity is high, and seek water damage restoration after all floods. If you suspect that your home has a mold problem, don't put the health of your loved ones at risk. Contact HVAC contractors with mold abatement services immediately.