Why Does Mold Form Around Air Conditioning Vents?

When you see mold or mildew around your air conditioning vents, you're probably wondering where it comes from. After all, the air that blows out of the vents is supposed to be dry. However, mold means there's moisture somewhere, so you need to start looking for what is getting wet, staying wet and encouraging mold to grow. Here are some frequent culprits.

1. Faulty Condenser

One major component of the outdoor condenser is the compressor, which turns a gas (air) into a liquid (water). There are also other important components that condensers use to pull moisture out of the air, and when one or more of them is faulty, you can end up with air that is simply not dry enough and an environment that's perfect for mold.

2. Wrong-sized Air Conditioner

You might think that an oversized air conditioning system would do more to cool the air and remove moisture, but it isn't necessarily true. A properly-sized unit cools and dries the air. However, a unit that's too large will cool the air faster than it needs to. Because the thermostat says it's sufficiently cool, the unit shuts off, but it hasn't had enough time to dry the air. When the weather is especially humid, this moisture lingers in the air and can build up and create the perfect environment for mold in the ducts. When the unit turns on again, it blows the mold spores through the ducts and they land on and around the vents.

3. Leaks

Holes anywhere in your home can enable water to reach your ductwork or insulation, providing one of the growing conditions for mold: a moist environment. Leaks can be holes or cracks that allow water or moisture to enter, or they can simply be areas where cold air can come in contact with a part of your air conditioning system, such as a partially open or poorly sealed window. The cold air can cause condensation to form, introducing moisture to the system.

4. Dust

Dust in the ductwork provides the other growing condition: a food source. Dust can come from clogged or poor quality filters, or filters that don't fit properly. It can never really be completely eliminated, so any time water or moisture infiltrates the system, mold can feed off the dust, multiply and be expelled onto the register.

Mold spores and dust are ever-present in the environment, but when certain conditions are met, they combine and the spores multiply to the point that they cause problems. Air conditioning systems need to create the proper balance of temperature, humidity and dust control to keep mold at bay. Faulty compressors, too-large units, leaks and poor filtration are the usual culprits, but there could be more. If you have discovered mold near your vents or registers it's a sign that something is wrong, so have an air conditioner repair service inspect your system to find the sources of the problem and eliminate this unsightly condition. Learn more about air conditioning by reading more on this blog.