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Last updated on January 20th, 2021 at 12:20 pm


Is there mold lurking in your air ducts? For many homeowners, an unseen health hazard could be a major threat to health and well-being. While most homes likely do not have dangerous levels of mold, some do — and if you think you smell that telltale scent, it’s time to find the source.

What Is Mold?

Mold is a fungus that can be found both indoors and outdoors. It consists of tiny organisms that are often black, white, green, orange, or even purple. In small quantities, mold spores are usually harmless, but they can easily grow and become dangerous if they land in the right conditions.

There are tens of thousands of species of mold, but most grow best in damp and humid conditions. You may find mold in damp areas of your home or on dead leaves and plants outdoors. Some mold spores can survive harsh, dry environmental conditions as well.

Many people are sensitive or allergic to mold. If you experience symptoms like a stuffy nose, red or itchy eyes, or respiratory stress and can’t pin down the source, you may be sensitive to the mold in your environment. People who have a weakened immune system from cancer treatment, organ transplant, or other causes are more likely to get mold infections.

It’s impossible to completely avoid mold, but there are actions you can take to reduce your exposure. Removing mold from your home and avoiding areas like compost piles and damp wooded areas could help control any symptoms you may experience.

Can Mold Grow in Air Ducts?

Mold can definitely grow inside air ducts. Significant amounts of mold in air ducts are not very common in most parts of the country, but we tend to see a bit more of it here in the Greater Seattle area due to the wet, moderate climate.

Mold grows particularly well in dark, moist areas. In many cases, mold growth is spurred by a water leak or standing water inside a duct. Any excess moisture or humidity increases the chance that there’s mold nearby.

Many homeowners do not know there’s mold in their air ducts until well after they would find it in other parts of their homes. It’s easy for mold to grow undisturbed in parts of your home you don’t normally see.

How Do I Know If There’s Mold in My Ducts?

mold in system air conditionerThere is almost certainly mold somewhere in your home, although it may not be dangerous. Hilary Karasz, a spokesperson for Public Health—Seattle & King County, has stated it’s impossible to completely eliminate mold spores from the indoor environment, especially in a wet climate like the Pacific Northwest. However, substantial amounts of the wrong type of mold could cause serious health problems for you and your family.

In some cases, you may be able to see the mold with your naked eye and smell its presence. Dangerous mold often takes the forms of black, green, or white spots. Noticeable quantities of mold can be a major health hazard, so you should take steps to remove it as soon as possible.

However, problematic mold is not always visible. It’s quite possible that your home has toxic mold hidden behind the walls in areas you can’t easily see. If you are concerned about mold but aren’t sure whether you have it, you can hire a mold tester to check.

Be aware that there are plenty of substances that look like mold but are actually something else. If you see something that you think might be mold, but you’re not sure, you can send a sample to a microbiology laboratory to get it tested.

Ultimately, the only way to know the extent of mold in your home is to get your air ducts tested by a professional.

What Should I Do If There’s Mold in My Air Ducts?

If there is substantial mold in your air ducts, you should take immediate action to remove it. One of the best ways to do this is to find a professional duct cleaner to do a thorough cleaning.

Professional duct cleaning generally involves using a strong vacuum and brush to remove particles from the ductwork. This equipment helps knock contaminants loose from the ducts and permanently remove them from your home. A true professional will take precautions to protect the surrounding carpeting and furnishing and inspect the entire system to ensure there isn’t asbestos they could potentially disturb.

You should expect a good duct cleaning to take a few hours, depending on the size of your home and duct system. There may be moderate noise throughout the vacuuming process.

Preventing Future Mold Growth in Your Air Ducts

If mold is growing as a result of a water leak or other structural issues, you will need to fix that problem in addition to removing the mold. Failing to address the root cause will just lead to the mold coming back. You may need to replace parts of your air duct system that are wet or moldy.

To avoid mold in the future, try to keep humidity levels below 50%. An air conditioner or dehumidifier could help during humid months. You can also clean bathrooms with mold-killing products, add mold inhibitors to any new paints you apply, and get your ducts cleaned semi-regularly by a reputable air duct cleaning company.

air duct cleaning before and after

Once your air ducts are free of mold, you can avoid future mold growth by having your air ducts and HVAC systems regularly cleaned. The National Air Duct Cleaning Association (NADCA) especially recommends frequent duct maintenance for households with shedding pets, smokers, or residents with allergies or asthma.

Professional Duct Cleaning in the Pacific Northwest

DuctVac Northwest is an indoor air quality company with 20 years of experience serving clients just like you. We are certified by the National Air Duct Cleaners Association (NADCA) and committed to best practices and integrity. We are not in the market to sell you a new furnace and unnecessary parts, just to provide you with healthy indoor air for your home and business.

We serve King, Snohomish, Pierce, Whatcom, Skagit, Island, San Juan, and Kitsap counties. Contact us today for a free consultation.