You might begin to notice musky smells coming from your heat and air registers. This musky smell is the smell of dirt, mold or mildew inside the vents. You can remove the smell and prevent it from getting there in the first place using several methods.
About Mold and Mildew
Mold and mildew tends to grow in areas with excess moisture because mold and mildew are plant spores that need water to survive. Mold and mildew spores always float around your home, but they will only grow when they land in an area with a water supply.
Preventing Mold and Mildew
You can prevent mold and mildew by solving the moisture issue in your home, which will be very difficult if you live in a humid climate where mold is common. Do this by fixing your ventilation system and by installing a dehumidifier in your home.
Cleaning Mold and Mildew
Bleach can help you remove mold and mildew from the surface of your vents. Bleach will not kill the mold or mildew spores, but will dislodge them from the surface of the heat and air registers. To use bleach, mix 1 cup of bleach with 1 gallon of warm water. Spread the solution over the surface of the vents, and scrub it off with a stiff-bristled brush.
Excessive mold and mildew growth can cause both long and short term health issues, which is especially true of susceptible individuals, such as pregnant women, the elderly, young children and those with respiratory issues such as asthma. Health issues include chronic hay fever-like symptoms, asthma or lung infections.