Why Does Mold Grow Within HVAC Systems?

Mold is a common household issue, but many people don’t realize that mold frequently grows in HVAC units. Mold on walls, windows, and other areas within your home is a potentially serious concern because it exacerbates asthma and other respiratory conditions, irritates allergies, and causes several other symptoms such as headaches, fatigue, memory loss, and shortness of breath.

When mold is within HVAC systems, the spores are spread further and more often due to the forced airflow, worsening the issue substantially. To help combat mold growth within your HVAC unit, it’s vital to understand why it grows there and how to prevent it in the future.

Moisture in HVAC Units Starts the Process of Mold Growth

Almost every type of mold in the world needs moisture in order to grow. If you’ve ever had mold in your house, you’ve likely noticed that it typically only grows where moisture has built up, such as in the bathroom, the kitchen, or in places that have experienced water damage like the basement or your garage.

Moisture accumulates in HVAC systems because the air conditioning unit also acts as a dehumidifier and pulls moisture out of the air in your home. That moisture moves through the entire unit until it’s ejected out of the house, but not all of the water is able to leave the system. Moisture also builds up if the system is in a warm environment and the unit has been shut off for prolonged periods of time, which doesn’t allow the moisture to be evaporated and removed properly.

HVAC Systems Provide Mold With the Warmth It Needs to Thrive

Contrary to popular belief, mold doesn’t need high levels of warmth in order to grow. Most types of mold only need temperatures above freezing to survive. Higher temperatures (within 60 to 90 degrees Fahrenheit) provide the absolute best conditions for growth and spreading spores. The aim of HVAC systems is to keep your home at a comfortable temperature throughout every season, and most comfortable room temperatures lie within the ideal range for mold growth.

There Is Plenty of Food for Mold in HVAC Systems

Mold needs food in order to sustain itself. It can feed on nearly any organic material it can find, making it very resilient and adaptive to a wide variety of environments. HVAC systems, despite being entirely inorganic, wind up with plenty of organic materials in their ducts and other areas for mold to feed on, such as dust, dander, pollen, hair, skin particles, and much more.

HVAC Systems Provide Plenty of Oxygen to Keep Mold Alive

Like most living creatures, mold needs a constant supply of oxygen in order to survive. HVAC units, which are constantly circulating fresh air throughout numerous parts of the system, provide more than enough oxygen to keep mold alive indefinitely.

How to Tell When There’s Mold in Your HVAC System

Unlike most instances of household mold where you can usually see spots of it on the walls or on the floors, mold growth within an HVAC unit is much harder to notice. However, there are some key indications that there is mold growing within your HVAC unit.

  • A musty smell whenever the unit is turned on
  • Black dust specks lining the vents of your HVAC unit
  • Splotches of mold on the outside of the air ducts
  • Increased severity of symptoms involving allergies, asthma, and other respiratory issues in the household

If you don’t notice these signs but you’re still concerned about possible mold growth within your HVAC system, grab a flashlight and look inside whatever vents and ducts you can inspect without disturbing anything. Any further inspections should be done by a professional HVAC service. This ensures that the unit is disassembled, analyzed, and reassembled properly to avoid any complications with the system.

The Most Common Spots Where Mold Grows Within an HVAC System

Mold can grow nearly anywhere within an HVAC system as long as the previously mentioned conditions for mold growth are present in that area. However, there are several spots within all HVAC units where mold growth is most common.

The first area where mold commonly grows is the condenser coil. When the air conditioner runs, warm air flows over the coil. When the warm air meets the cold coil, it causes condensation to form. Additionally, dust and other organic material that flow through the ducts wind up on the coil. Much of the moisture that accumulates on the coil drips off, but some of it remains on the coil and creates an environment where mold can easily grow.

The second area where mold thrives is the drain pan. The moisture that drips off of the condenser coil goes into the drain pan where it is collected and disposed of outside the home. Like the coil, not all of the moisture is removed from the drain pan as the water moves off of it, especially if the pipes that lead the water outside are clogged. The dust and other organic debris from the coils also drip down into the drain pan, creating another environment where mold grows quickly and easily.

The next area with a high chance of mold growth is the air ducts. Some moisture gets into the air ducts through the natural humidity in your home as the unit circulates the air. Air ducts connected to the bathroom and kitchen frequently accumulate an abundance of moisture due to steam being removed while cooking and during showers. Additionally, moisture can get onto or into the ducts due to nearby leaking pipes. The air ducts are also the first stop for all of the dust and other organic substances that are sucked out of your home. All of these factors create a suitable environment for mold.

Finally, mold commonly grows in your whole-house humidifier. In order to prevent your home from becoming overly dry in the winter months, your whole-house humidifier pumps a moderate amount of moisture into the air by running the air over a pan filled with water or a soft pad saturated with water. The humidifier has a filter to trap dust and other organic debris as the air flows through, providing mold with the water, warmth, and food that it needs to grow. Changing the filter regularly helps cut down on the chances of growing mold in the humidifier, but it is still a prime location for mold to thrive.

Mold issues within your HVAC system are tricky to identify and effectively treat without the help of a professional. If you’re experiencing a mold problem or other issue in your HVAC system in the Greater Houston area, you can rest assured that our team of skilled professionals at The Lee Thompson Co. will be able to solve your problems quickly, easily, and at an affordable price.

In addition to ridding your system of existing mold, we offer repair, installation, and maintenance services for air conditionersfurnaces, heat pumps, and ductless systems. We also provide duct sealing and cleaning and indoor air quality solutions. To learn more about our HVAC services and products, contact The Lee Thompson Co. today.