When you turn on your AC unit on, have you ever noticed a smell reminiscent of old stinky socks or a sweaty locker room? This is a very real problem, and not one you can solve simply by lighting a scented candle. Then your house will smell like socks and lavender – still gross. Here's what causes this smelly problem and how you can fix it.

What Causes This Phenomenon

The stinky smell is usually most noticeable when you first turn on your air conditioner, and is more likely to happen early in the cooling season. Over time, dust collects in your air conditioner's filtration system. Because the inside of your unit is nice and dark, and usually moist, mold and bacteria begin to grow on the evaporator coil. When you turn on your air conditioner, the cool air that fills your home is loaded with the smell of that mold and bacteria.

Where To Check

There are some simple things you can do to help eliminate the problem.

• Check the filter inside the air conditioner. Is it filtering properly, full of gunk or wet? It it is, time to replace that old filter with a new one.
• Check the drainage pans for water and empty them completely of any water. While you're poking around, clear out any visible blocks from the drain.
• If you can, take a look at the drainage lines leading to the pans. You can purchase tablets that dissolve and help keep the lines clear. A little bit of water is normal, but a whole lot of water is a problem.

After checking these areas and you can still smell mold, then bacteria and mold are thriving happily on the evaporator coils and need to be cleaned thoroughly. Here's how:

1. Turn off the AC unit at the thermostat and the circuit breaker.
2. Open the panel on the AC unit to expose the evaporator coils.
3. If you want to, vacuum out all the dirt and dust first.
4. Mix one part bleach to three parts water, and scrub the evaporator coils with an old brush to remove the mildew and mold.
5. Thoroughly dry the coils and immediate area as much as possible.

Prevent Future Growth

Now that your air conditioner is clean, you want to keep it that way by not letting mold or bacteria get onto the evaporator coils all over again. One way to do this is by investing in high quality air filters that are more capable of filtering out tiny particles. Another solution is to buy a UV air purifier. These work by killing bacteria and mold spores using UV, and are a good thing to have if anyone in your home has asthma or allergies.