Solved! Here’s Exactly How To Treat Mold in HVAC Systems

Q: I’ve noticed a musty smell each time my air conditioner turns on. Do I have mold in my HVAC? How do I get rid of it? 

A: A musty, moldy scent or allergy symptoms that occur when your air conditioner is running could be a good indication of mold in your HVAC unit. To get rid of mold, you’ll first need to have the unit or units inspected to see the extent of the issue and determine the treatment plan. This way, a professional can locate the mold and recommend a variety of options, from the best air duct cleaning services to the best mold removal companies. If you’d like to take the DIY route first, you can consult the steps below to help you identify signs of mold and how to get rid of it safely.

Mold in HVAC systems needs to be addressed promptly to avoid spreading mold spores around the home through the air vents.

Whether a homeowner sees signs of mold on the surfaces of their HVAC system or notices that their AC smells musty when it kicks on, these issues should be dealt with quickly in order to avoid the further growth of mold or physical symptoms that affect the health of those who live or spend time inside the home. If the issue isn’t addressed right away, it could cause mold to contaminate the entire system and spread through the vents and the air in the home. When this happens, it can lead to allergy-like symptoms such as coughing, wheezing, shortness of breath, and chest tightness. Mold is especially harmful to those with respiratory conditions, compromised immune systems, or pre-existing lung diseases, which is why it might be a good idea for those who have these conditions to get their home or HVAC systems inspected for different types of mold.

There are three areas of an HVAC system where mold can grow: the air ducts, the evaporator coil, and the drain pan.

A common place mold grows in HVAC systems is the air ducts, especially if the ductwork is poorly sealed or insulated. This makes the ducts more prone to condensation, which can provide the ideal environment for mold growth. The evaporator coils of an HVAC system are responsible for cooling the air, which is why condensation on the coils that is not properly drained or dried can lead to mold growth on the moist surfaces. Another spot conducive to mold growth is the drain pan, which collects and drains condensation from the HVAC system. If the drain pan is not regularly cleaned or if drainage issues exist, stagnant water can accumulate and lead to mold growth.

Some common causes of mold in an HVAC system include leaking ducts, an oversize AC unit, excessive humidity in the home, and poor ventilation.

Mold thrives in areas with high moisture, which is why any kind of leak or excess moisture can cause mold in an HVAC system. Leaky or damaged ducts, for instance, can allow moisture to enter the HVAC system and lead to mold within the ductwork if the moisture is not properly drained or dried. Poor ventilation is another common cause of mold, since it can lead to stagnant air and moisture accumulation. Without proper airflow, moisture can linger, allowing mold spores to settle and grow.

In addition, if an HVAC system is not maintained properly or filters are not cleaned or replaced, a homeowner can expect to find an accumulation of dust, debris, and moisture, which makes for an excellent breeding ground for mold—and an unpleasant environment for residents who have allergies to dust and mold.

There are several signs of mold in an HVAC unit, including a musty smell, visible mold on air vents, and unexplained respiratory symptoms in residents.

Once a homeowner knows what mold smells like, they’ll be able to tell whether the smell coming from their HVAC system is mold or something else. A persistent musty or moldy smell in the home or an unpleasant odor coming from the vents or when the system is running could be a sign of mold in the air ducts, on the evaporator coils or condenser coils, or on the air filters. If a homeowner doesn’t notice a musty smell or wants further proof of mold growth in their HVAC units, they can check the air vents, ductwork, coils, and drip pans for any signs of mold spores. Any dark spots, discoloration, or fuzzy patches indicate visual mold and confirm that the homeowner needs to consult a mold remediation or HVAC specialist to service their units and remove any signs of mold. Knowing what black mold looks like can help homeowners successfully identify it and take care of it before it gets worse.

Another indication that mold is in an HVAC unit is if the homeowner or others in the home experience health issues, especially if they occur when the unit is running. Any allergic reactions such as sneezing, coughing, congestion, watery eyes, or worsening asthma symptoms when the HVAC system is running could be a sign of mold in an air conditioner or heater. In this case, it’s best for the homeowner to have their system looked at as soon as possible in order to ensure any affected occupants don’t continue to have a variety of health problems associated with mold that can negatively affect their physical health.

You can confirm the presence of mold in the HVAC ducts with an at-home test kit or by calling a professional mold inspector.

The good news is that if a homeowner suspects mold in their HVAC system, they can test for mold at home using a testing kit to either confirm their suspicions or relieve their concerns. Most of these kits test for the presence of mold in the air, however, so they may not be as helpful if the homeowner is trying to determine if the mold is actually in their HVAC ducts. If a homeowner suspects mold but is unable to identify it visually or by smell, or they find at-home kits unreliable, it may be necessary to hire one of the best HVAC companies or a mold remediation specialist. A professional can conduct a thorough inspection of the HVAC system and perform testing to confirm the presence of mold. Testing may involve taking air samples, surface samples, or swab samples to be sent to a laboratory for analysis.

Removing a small mold infestation in an AC unit could be a DIY project, but professionals have the correct tools and experience to address the problem quickly and safely.

In some instances, it’s reasonably safe for homeowners to tackle mold removal using a DIY method like vinegar to kill mold, but it’s important for them to know the factors that determine whether they should tackle the task themselves or hire a pro. The Environmental Protection Agency (EPA) says that any mold problem smaller than 10 square feet can be handled by a homeowner, but larger areas should be handled by a licensed professional due to the health risks. Cleaning solution and soapy water may not be enough to remove the spores from a mold-contaminated HVAC system, especially in a larger home. In this case, it’s best for the homeowner to call a professional for mold inspection and remediation; a pro will have the protective gear, tools, and treatment options that will keep the residents safe, which makes mold remediation costs well worth it. Homeowners may also want to budget for air duct cleaning costs to ensure their system remains mold-free.

You can help prevent mold from growing in your HVAC system by regularly changing the filter, consistently running the system, and getting annual HVAC inspections.

To avoid further health risks and ensure their HVAC stays mold-free, homeowners can use a few methods of mold prevention. Regular cleaning, inspection, and furnace filter replacement will keep any moisture or debris from building up and causing more harmful or expensive problems. Homeowners can also try to manage the humidity levels in their home, address water leaks quickly, and check on the system’s drainage to make sure everything is running smoothly. Having an HVAC professional perform an annual check on the system and do a mold inspection costs a relatively small amount and allows homeowners to stay on top of any work that needs to be done on the HVAC unit.