Mold gets into your home’s ductwork when there is moisture inside the ductwork. As your air conditioner circulates cool air through the air ducts on hot days, the humidity in the air can condense in the ductwork. The moisture in the air beads up on the walls of the ducts. The presence of this moisture allows mold spores to grow and colonize inside the ductwork.
Mold spores get into the ductwork by blowing in elsewhere in your home or from the outdoors. The warm moist environment in the ductwork can be an ideal place for mold to grow. When it is growing in your air ducts, the spores will be circulated through the mechanical equipment, blown through your system, and into the air throughout your entire home. This may be one of the biggest reasons why you need to clean your ductwork.
Signs you may have a mold infestation in the ductwork
The unmistakable signs of mold in the air ducts include:
- Moldy or musty odor throughout the house or in one or more rooms. The odor may become stronger when the air conditioner runs.
- Black mold is visible around the air vents, ducts, or in the air conditioner drip pans.
You may also experience health effects. The long-term effects of mold exposure on your health can be unpleasant, even dangerous. A black mold infestation in your air ducts can cause several of the following symptoms:
- Allergy-like symptoms such as watery eyes or itchiness in your eyes, irritated sinuses, runny nose, and/or throat irritation often get worse when the air conditioner runs.
- Headaches when you are home but nowhere else.
- Nausea, fatigue, or dizziness when you are home.
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DIY mold removal steps
Before you spend the time and money cleaning mold out of your ductwork, have the substance tested by a lab to determine that it is in fact mold. If you determine that it is mold, try to assess how extensive the growth may be. If it is extensive, you will probably need the help of a professional HVAC contractor to assess the extent of the problem and the best way to clean it out effectively. In some cases, the insulation around the ductwork will be infested and need replacement from an HVAC contractor.
If you believe the mold infestation has not established itself in a large area, however, you can remove it yourself and save a significant amount of money. Here are the steps you should take:
1. Find a mold removal cleaning agent and mold inhibitor. You can make your own mold cleaner by mixing one tablespoon of household detergent, 1/2 cup of baking soda, and 1 cup of water for porous surfaces. For non-porous surfaces (such as steel ductwork and vent covers), you can use 1 part bleach with 16 parts water. Pour the mixture into a spray bottle for ease of application. Alternatively, you can purchase an EPA-approved mold-killing product. Also, purchase an EPA-approved mold inhibitor to apply after the cleaning.
2. Wear protective clothing. Protect yourself from the mold-killing agents you are using and the mold itself. The EPA recommends wearing an N95 mask, and you should wear rubber gloves, coveralls, and protective eyewear.
3. Turn the power to your HVAC system off. You will need safe access not only to your ducts, but also to your heating and cooling units, evaporator coil, and drip pan. Your system needs to be powered off.
4. Choose your removal option:
(1) Scrub and vacuum. If you choose this option, soak the moldy areas in your ducts and around your vent openings with your cleaning agent. Let it soak for five minutes. If you are using a commercially prepared mold killer, follow the manufacturer’s instructions on the product label. Use a brush or rags to scrub the area in circular motions to remove the mold. Soak up excess solution with paper towels. You should vacuum the area as an added precaution. Dispose of your mold removal rags by double-bagging them in 6-mil or thicker trash bags. Remove all disposable air filters and dispose of them in the same manner. Clean or replace every vent cover and register. (Try washing one on the sanitizing cycle in your dishwasher – if it works, do them all that way and save yourself some labor).
(2) Rent a mold removal fogger machine. You can rent or purchase a mold fogger from a hardware store. High concentrations of mold control chemicals have been shown to kill mold spores. The fogger atomizes a mold control solution into a fine mist for even surface application.
If you choose this method, follow any directions from the manufacturer. You will probably need to cover all of the heating/air-conditioning vents in your home. You can use small cut-out pieces of cardboard and masking tape to keep them covered while you kill the mold in the ductwork. Leave one vent open to access the ductwork.
5. Apply the mold inhibitor. Once the ductwork has been cleaned, follow the manufacturer’s instructions and apply the mold inhibitor to all of the components of your HVAC system. This will help mitigate any new mold growth.
6. Install new filters. Install new air filters.
7. Monitor for new growth. After you have completed this process, keep a lookout for new mold growth. If you see it coming back, do it all over again. If the mold keeps coming back, you should probably have the system professionally evaluated for a hidden mold or moisture problem that needs to be repaired.