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Why Is My Furnace Filter Black?

Is it time to have your furnace checked by professionals? At BVS Home Experts, we’re always ready to tackle your furnace repairs. Call us at (281) 609-3650.

If you change your filter regularly, you might be shocked to discover a black furnace filter when you replace it. You might gasp and ask aloud, “Why is my furnace filter black?” A black filter can indicate a few things happening within your home. 

Sometimes, the dirty filter points to something harmless and typical. Other times, you could have a dangerous problem that requires a professional. As the top providers of furnace installation in Katy, TX, our experts have seen it all. 

We put together the following list of reasons furnace filters might turn black. Read on to find out whether you can relax or need to address a serious issue. 

What Does a Furnace Filter Do?

Many homes have split systems, meaning the air conditioner is separate from the furnace. As an air filter cleans air circulating through your AC, the furnace filter works similarly when you use your heat. 

Furnace filters trap and remove particles of dirt and dust from the air they intake. They also remove allergens, viruses, and mold, resulting in cleaner air inside your home. 

All filters have a MERV (minimum efficiency reporting value) rating. A filter with a higher MERV rating will remove more and smaller particles than filters with lower ratings. You should replace your furnace filter every three months for optimal performance. 

While you may understand how furnace filters work, you still wonder, “Why is my furnace filter black?” You’ll find several answers to this common question below. 

Carbon Monoxide Collection

When you notice that your filter has turned black, you should immediately test your indoor carbon monoxide levels. Sometimes, furnaces don’t work correctly, leading to a carbon monoxide leak. 

Carbon monoxide leaks can have deadly consequences. They can also go unnoticed since they don’t emit smells or sounds. A CO detector may alert you to this issue. If you don’t have a detector, call us immediately to test your house for carbon monoxide leaks. 

Soot in the Area

Since furnace filters clean indoor air, they’ll remove soot particles. Soot can have many sources. A few things that produce soot indoors include:

  • Fireplaces
  • Gas-powered appliances
  • Candles
  • Incense

If you leave your door open, soot can travel indoors from bonfires, leaf fires, and grills. While leaving your backdoor open during a barbeque or a bonfire party may be convenient, your furnace filter gets dirtier more quickly. 

If you can trace the problem to gas-powered appliances, you should seek repairs. Otherwise, avoiding soot buildup requires less frequent use of candles, incense, and fireplaces. You can also change your filter more often to mitigate the issue. 

Mold Growth

Sometimes, a house provides the perfect environment for spores to flourish. For example, a wet, dirty evaporator coil creates conducive conditions for mold growth. High levels of humidity in your home can also cause mold problems. 

Even when you repair the source of the problem, mold can prove a strong adversary. It can cause respiratory problems and trigger allergies. Once you have addressed the central issue, hire professional cleaners to eliminate the mold. 

Dirty Furnace Filter

A dirty furnace filter harms your HVAC system. If you haven’t changed your air filter in a long time, your air filter may turn black from dirt, dust, and other debris. In such cases, you should change your filter more frequently. 

Old filters force your furnace to work harder to circulate air. Your furnace must fight against caked dust to pull air through, which overworks your HVAC system and increases wear and tear, leading to more maintenance issues. 

Additionally, you’ll have poor indoor air quality. When old filters don’t function properly (or at all), old particles escape and re-enter your home’s atmosphere. Dirty filters can increase allergic reactions and respiratory issues if you leave them unchecked. 

Clogged Vents

Sometimes, obstructions form inside your vent system. These clogs usually occur out of sight, forcing your HVAC system to work harder to circulate air. 

Sometimes, you can clean a clogged vent yourself. Check your grates for dirt or dust. If the grates are dirty, cleaning them may solve the problem.

Damaged parts or debris can create sooty emissions, posing a fire hazard for your home. Other times, foreign objects or HVAC components may get in the way. You’ll need help from HVAC experts in such cases. 

Why Is My Furnace Filter Black, and What Should I Do?

A black furnace filter is an abnormal occurrence requiring swift action. Even if you suspect you know the reason behind your black filter, you should call an HVAC service provider to perform a checkup. An expert will address problems like:

  • Carbon monoxide leaks
  • Soot intakes from dangerous sources
  • Black mold
  • Obstructed ventilation systems
  • Faulty furnace components

If none of these things pose a problem, you’ll have confirmation and peace of mind. If your furnace filter turns black because of fireplace soot or burning candles, reduce how often you use these to eliminate soot buildup. Otherwise, you will need to adjust your replacement frequency. 

Pets, multiple occupants, and frequent furnace use will also contribute to a filter’s buildup. A filter change every three months is a general rule. However, homeowners should adjust the frequency to their household needs. If you have multiple factors that contribute to a level of pollutants in the air, you should change your filter more frequently.  

Call Our Home Experts for Furnace Repair in Katy, TX

“Why is my furnace filter black?” Call our experts at BVS Home Experts to find out! We can confirm that your furnace works safely, prevent dangerous conditions, and perform routine maintenance. You can also read our furnace maintenance tips to improve how you care for your HVAC system.

Contact us at (281) 609-3650 to have your furnace issues resolved or schedule a routine maintenance appointment in Katy, TX.

Author Bio:

Ronald Via

Ronald is one of the key contributors to BVS Home Experts, a family-owned and operated full-service air conditioning and heating company serving the Katy and West Houston areas. With a deep understanding of air conditioning and heating concerns, Ronald brings a wealth of knowledge to our readers.

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