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Mold is most common in the summer due to humidity and precipitation. However, that doesn’t mean that your home is immune to mold problems during the winter and a mold inspection during this time of year is a good idea before holiday guests arrive. 

In fact, a furnace can be a major contributor of household mold problems during the winter. When you turn the furnace on for the first time during the winter, you introduce a new air source into your home. Oftentimes, this new circulating air brings with it fungi, bacteria and other particles – like mold – because the furnace has been out of use for such a long time. 

The good news is that metal is not the most common surface for mold to grow. It usually prefers organic materials like wood, drywall, and, of course, damp surfaces like the shower and tub. But given the right conditions, mold can grow anywhere, including your furnace or HVAC system. 


Mold isn’t particular about where it forms a new colony. The main things mold needs in order to thrive are moisture and food. Both can be found within a furnace. Moisture is usually the result of a leak. Condensation leaks are particularly common in furnaces. Mold can feed on practically anything, including dust that accumulates through the summer and that collects on the furnace’s air filter. 

The other thing that mold loves is to be left alone. Dark, warm places are very often the home to undetected mold colonies. Inspecting dark, hard-to-reach areas often is the best way to prevent a major mold problem in your home. 

How to Detect and Prevent Mold in Your Furnace 

Looking for mold in the basement or attic is easy enough. It’s probably going to be in an obvious location or can be identified by the homeowner. 

These things aren’t true of mold in tight areas like the furnace, HVAC system or plumbing. Mold is hard to find and even harder to remove in these areas. You will require professional assistance to find mold and to get mold out of your furnace, so the sooner it is discovered, the sooner Pure Maintenance of St. Louis can help. 

To give you a head’s up about this potentially dangerous problem, here are a few signs that you have mold in your furnace:

  • Odor – Mold gives off a musty odor, different from the dusty odor that you may smell when you use your furnace for the first time. That smell should only occur initially, but it shouldn’t persist beyond this first few uses. Mold, on the other hand will continue to emit a must odor as long as it is present. 
  • Visible mold – Mold in another part of your home often indicates that there is hidden mold somewhere else. One has often led to the other, and although it’s impossible to tell which came first, but all mold colonies need to be identified and removed to protect your family from sickness. 
  • Allergy symptoms – If anyone in your home starts experiencing classic mold allergy symptoms, it’s likely that there is mold in your home. These symptoms include frequent headaches, itchy skin, coughing, sneezing, and shortness of breath. Unfortunately, these are symptoms that are commonly associated with many respiratory disorders, so it’s hard to diagnose a mold allergy without doctor-administered tests. 

The problem with these signs of mold growth is that they are not 100% accurate indicators that there is mold in your furnace – or anywhere else, for that matter. They only indicate that there might be mold. The only way to know for sure if there is mold inside the furnace is to have it inspected. 

You may think that mold in your furnace is fairly benign because it is contained in a small area. But if you know anything about how furnaces work, you know that they circulate warm air throughout your home. Microscopic mold spores can travel on that air to any heated area of your home. 

It’s common for homeowners to have perpetual mold issues once they have seemingly treated visible mold. This is a strong indicator that there is an undiscovered mold source in your home. 

If you find yourself in one of these cycles, constantly finding and treating mold in your home, it’s time to get a professional involved. Pure Maintenance of St. Louis is familiar with all the places mold can hide, including the furnace and ducts. 


If you suspect a mold problem, schedule a mold inspection from Pure Maintenance of St. Louis sooner rather than later. A mold issue in your home could result in weakened building materials and unexplained illnesses for your family and even pets. 

Having a full home mold inspection is the only way to put your mind at ease when it comes to both visible and hidden mold. Professional mold companies test the air in your home to determine if the levels are out of normal range. If high mold levels are found, they will begin searching for the cause – usually a mold colony somewhere in your home. 

Our mold specialists have equipment that can inspect the inside of pipes, ducts, furnaces and more. No area is hidden from our team! 

Once the source of mold is discovered, our team will safely remove it from your home. Precautions are taken to prevent mold spores from spreading to other areas of the home and a post-removal inspection is performed to ensure that all of the mold has been removed. 

Your mold pro may also recommend mold remediation if mold levels are extremely high in your home. Remember that some mold is expected to be indoors, but levels should be minimal. When you have a recurring mold problem, the issue may be that your home is sealed too tightly, which doesn’t allow for ventilation that would release excess mold spores. 

Mold remediation is a service that filters out excess mold and reduces the risk of recurring mold issues. 

If you have noticed any of the signs above, it’s well worth your time and money to have a professional mold inspection done by Pure Maintenance of St. Louis. 

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