Do you dread the hottest part of the day because turning on the air conditioner triggers the release of a musty odor reminiscent of dirty laundry? Instead of avoiding the thermostat, track down the cause of the problem and treat it. Letting an odor issue go on for months or years could compromise your health and damage your air conditioner, not to mention embarrassing you in front of summertime guests.

What to Suspect

Anytime you smell a distinctly musty odor emanating from your air vents, it's most likely mold or mildew growing somewhere in the HVAC system. These lifeforms release their distinct dirty sock odor as they spore, and those spores are very irritating to your sinuses and lungs. If you have family members with asthma or allergies, that musty smell indicates they're being exposed to triggers that will worsen their symptoms and could set off a serious attack. For very sensitive asthma sufferers, mold growing in the air conditioning system could threaten their life.

Where to Check

Of course, the air conditioning system is large and complex due to the dozens of feet of ductwork snaking through your home to deliver the cool air. There are a few places in the system more likely than the rest of it to contain mold and mildew growth. Start your search for the source of the unpleasant musty smell by checking the

• Condenser coils, which stay humid during operation and can feed mold when they get covered in dust and dirt
• Filters, which can harbor mold growth when they're not changed regularly
• Drip pan and its drain, which are regularly full of the moisture needed for thriving mold growth
• Duct work, which can become wet due to malfunctioning air conditioner equipment or a leak elsewhere in the home.

An HVAC technician with a flexible camera system can check all of these areas in a single afternoon to quickly determine whether mold is your problem or not. If you suspect it's mildew but there's no fuzzy growth on any of these four areas, invest in a more thorough search to make sure the mold is not hiding in the insulation wrapped around the ducts or in a part of the A/C unit that usually stays dry.

How to Treat

Finding the mold isn't enough; you must eradicate it as well and keep it from coming back. Bleach is no longer considered safe for use in HVAC systems, so hire a professional to use a biocidal spray that is EPA-approved to kill all the existing colonies of mold. Even if the mildew was growing on a filter or other part that was removed and replaced, you should have the entire system treated to kill off spores that spread before you discovered the problem. Don't try to treat the mold yourself, or you could end up hurting yourself with the cleaning chemicals you choose.

It's likely that the mold will return again unless it was linked to a very specific and fixable cause, such as a clogged drain pan or a leaky pipe above a duct. Installing an ultraviolet treatment light inside the air conditioning unit stops mold from developing and can save you a lot of money on routine treatments if you live in a humid, dusty area.

When to Inspect

Don't wait until you smell a musty odor to have your system inspected for mold growth if it's a big deal in your household due to allergies and asthma. In a humid climate, have your air conditioner inspected twice a year specifically for mold growth. Your A/C technician can add it on to the usual maintenance visits to make sure any mold growth is caught as early as possible. For more information, contact an air conditioning repair company like A Bailey Plumbing.