Does an AC Kill Mold?

No, an air conditioner does not kill mold. What it does is remove moisture from the air, and because mold needs moisture to grow, a properly working AC makes your home a harder place for mold to get started. Once mold has taken hold, cooling the room will not remove it.

We live in a dry part of Washington, so mold is less common here than in wetter regions. It still turns up, usually where a specific leak, damp corner or poorly ventilated space gives it what it needs.

How mold gets started

Mold spores are everywhere, indoors and out. They stay dormant until they land on a surface that stays damp for long enough, and they feed on organic material such as drywall paper, wood, dust and fabric. Warmth helps, and so does still air. The conditions that matter most are moisture and time.

In a house, the likely spots are bathrooms without a good exhaust fan, laundry rooms, basements and crawlspaces, areas around leaking pipes or windows, and the space around a slow roof leak. Anywhere that stays wet for a day or two is worth watching.

Wildfire season can add a wrinkle, because people close up the house for days and run the AC constantly. That is fine, but shower steam, cooking and wet laundry all add moisture to a sealed home, so keep the exhaust fans running. Homes that sit empty for a few weeks in summer with the AC off can also grow a musty smell, and a quick look under sinks and around the water heater when you return is a good habit.

How your air conditioner helps

As warm air passes over the cold indoor coil, water vapour condenses and drains away. That lowers the humidity in your home. Keeping indoor humidity moderate makes it harder for mold to establish itself on walls and furnishings. A system that is sized correctly runs long enough to do this properly, while a unit that is too large cools quickly and shuts off before it has dried the air.

The AC also needs to be free of moisture problems itself. A condensate drain line that is clogged can back up and leave standing water in the drain pan, and a dirty, damp coil is an inviting place for growth. That is one more reason for an annual tune-up, where a technician cleans and checks those parts.

Things you can do

• Replace filters on schedule so the coil stays clean and airflow stays strong.
• Run bathroom and kitchen exhaust fans, and vent dryers to the outdoors.
• Fix leaks promptly and dry wet materials within a day or two.
• Keep the area around the indoor unit and drain line clean and dry.
• Use a small hygrometer to keep an eye on indoor humidity.

If you spot mold

Small patches on a hard surface, such as a bit of grime in a shower corner, can usually be cleaned by the homeowner using ordinary household cleaning products, with gloves and ventilation. Fix the source of the moisture too, or it will return.

Larger areas, mold on porous materials, a persistent musty smell with no visible source, or growth around the HVAC system itself call for professional help. If you suspect mold inside your ductwork or on the indoor coil, do not run the system in the meantime and turn it off until a technician has taken a look. We do not test for or treat mold ourselves, but we can look at the equipment, correct moisture problems and tell you what we see. If you have health concerns about mold in your home, talk with your doctor.

If your air conditioner is running but the house still feels damp or smells stale, call Air-Tech at (509) 392-2021 and we will check the system over.