Mold in HVAC Systems


Visible mold on your drywall, carpet, or basement walls is trouble. But mold in HVAC (heating, ventilation, air conditioning) systems is a real danger to you, anyone living in your home, and even your pets (Yes, some pets are allergic to mold; they can have the same reactions to mold exposure as humans). If you have mold in your HVAC system, when your furnace or AC operates, the blower comes on and the airflow spreads mold spores throughout your entire home. Mold spores will contaminate every room and every space. The longer the system operates while contaminated, the worse your mold problem can become.

There are numerous health issues that are associated with mold exposure. Most of these issues are directly related to the respiratory system. They include asthma attacks, coughing, runny nose, sneezing, and other allergic reactions. Still other issues involve eye irritation, skin rashes, a general sense of fatigue or depression, shortness of breath, and a sore, scratchy throat. If any of your family members are feeling these types of symptoms, especially when they are in the home, you may have a mold problem that you’re not aware of.

Is Mold In Your HVAC System a Possibility?

If you can detect a musty smell in one or more rooms in your home, but there are no visible signs of mold anywhere, you may have a mold problem. Do the smells seem to be worse when the furnace of air conditioning is running? If so, the problem could be in your HVAC system. Mold spores are easily aerosolized, or suspended, in the air where they can be breathed in by the home’s occupants. Mold spores are not visible to the naked eye (they average in size from 10 to 30 microns, that’s smaller than the width of a typical human hair) and the best way to determine whether there is a mold contamination problem is to have your home and HVAC system tested through air sampling. Air sampling involves capturing a known volume of air and measuring the number of contaminants that are in it. The result will be expressed as parts per million. Here is a link for more information and a list of NADCA (National Air Duct Cleaners Association) qualified professionals in your area that can test your home and HVAC system for mold contamination.

Common Causes of Mold in HVAC Systems

mold in heating system

Moisture condensation is the largest cause of mold in HVAC ducts. During warmer seasons, cooler air is being piped through vents and sometimes moisture will condensate along the sides of the ductwork. This warm, dark, dusty environment provides an excellent breeding ground for mold.

Another common cause is improper sizing of AC systems. Your system may be over-sized or under-sized and this allows for inefficient operation of the entire system, which may lead to condensation issues.

Yet another problem is caused by condensed moisture gathering in the HVAC system’s drain pan or condensation line. Sometimes a simple clog will enable this trapped moisture to become an issue.

How To Remediate Mold in HVAC Systems

Before beginning remediation, you must find and eliminate the source of any excess moisture or water in the system. The next very important requirement is to shut off the HVAC system. You don’t want a blower to suddenly come on during remediation efforts. Containment of the HVAC system is always a concern and should be established at the start of any mold removal process. The last thing you need is to allow the spread of any mold spores to unaffected areas or rooms.

When cleaning mold, there are many types of chemicals and cleaners that can be used. That said it could be very tricky, not to mention dangerous, attempting to accomplish this task. Professionals have several different mechanical means of cleaning including brushes, blowguns, air whips, and vacuums to dislodge mold inside of air ducts and then to push or pull the mold into specialized collection devices. They also know what type of antimicrobial or biocide chemicals can safely be introduced into an HVAC system for cleaning and sanitation purposes.

DIY Remediation For Mold in HVAC Systems

Personal protection equipment, or PPE, is the essential first step for the do-it-yourself individual. Gloves, safety goggles, and a N-95 rated mask are required to ensure your personal safety while remediating mold.

Once again, make sure the system is shut down. Turn off the appropriate circuit breaker(s) to ensure that the furnace or air conditioning unit will not come on. Remove any furnace filters, bag them up, seal the bags closed, and dispose of them. Next, choose a cleaning solution containing baking soda, borax, or household detergent and mix it appropriately with water. (Use 1 teaspoon of detergent with ½ cup of baking soda and 1 cup of water; or use 1 part borax with 16 parts water). Fill a spray bottle with the solution.

Using a HEPA (high efficiency particulate air) vacuum, remove as much visible mold as possible. Then generously apply your cleaning solution on the moldy areas using the spray bottle and allow the solution to dwell for several minutes. Using towels that can be thrown away, wipe the areas where you saw the mold. Then repeat vacuuming with the HEPA vac. Sometimes you may need to repeat this entire process, especially if there was a lot of mold present. Don’t forget to bag the dirty towels before removing them to a trash receptacle.

Lastly, apply a mold inhibitor to control mold growth inside your HVAC system. Make sure that you use only EPA registered products that are intended for use on heating and cooling systems. Keep in mind that mold can grow in as little as 48 hours, so after a couple of days you should re-inspect your system.

EPA Recommendations and Warnings

The U.S. Environmental Protection Agency recommends hiring a professional HVAC cleaning professional if you suspect you may have a mold problem inside your HVAC system. The mold removal process is intensive and specific procedures need to be followed to ensure that safe, effective mold removal is accomplished. Also professional remediation companies have equipment, cameras, and training that the average homeowner doesn’t have.

A professional company will prevent the mold from returning in the future, while at the same time protecting you and your family from the many health issues that mold can cause. If you suspect a mold problem in your HVAC system, you really should consult with a NADCA certified HVAC mold remediation company. They can advise you of the options available to you to solve your mold problem. Even if you choose to do the work yourself, everyone can benefit from some free, expert advice. For a list of qualified HVAC professionals in your area that will provide you with a free, in-home inspection and remediation quote, follow the link.



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Written by Mark Huey.




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