Why Is My Furnace Filter Black?

December 15, 2016

Furnace filters are designed primarily to protect your furnace from dirt and debris that could harm it, but modern filters can also help to improve the air quality in your Cincinnati home. So if you find your air filter is black when you replace it, it can be quite concerning. Does this mean there is a problem with your home or your furnace? Not necessarily.

The Reasons a Furnace Filter May Turn Black

After several months of use, you may notice dust and debris starting to collect on the air filter for your furnace. This is normal, but if it turns completely black, there may be a problem. Here are the most common reasons a furnace filter may turn black:

  • Excessive dust and dirt: High amounts of dust, dirt, and debris may turn a filter black in rare cases, but this would mean the air filter is almost completely clogged. This can damage the furnace, so it is important to eliminate dust as much as possible. An air purifier may be a good option.
  • Candle or fireplace soot: If you burn candles or have a fireplace, small amounts of soot will be produced and distributed throughout your home. This can stain the air filter and turn it black, but in most cases this is harmless. Just be aware of the issue and replace the air filter before it causes furnace performance problems.
  • Carbon monoxide: If your furnace, water heater, stove, or any other fuel-burning appliance is not working properly, it may release carbon monoxide into the air anytime the combustion process is not properly completed. This gas is odorless, tasteless, and invisible, and it can lead to serious illness or death if you are exposed for too long. While carbon monoxide itself is invisible, the soot that is produced during incomplete combustion can stain the furnace filter, indicating that the gas is being produced.
  • Mold growth: If the furnace filter is too close to the evaporator or there is moisture inside the filter cabinet, mold can form on the filter. While most mold is harmless or may only cause moderate irritation, some, like black mold, can pose a serious health threat.

Can a Black Furnace Filter Make Me Sick?

If the filter has turned black due to carbon monoxide or mold, then yes, the substances that turned the filter black can make you sick. Carbon monoxide exposure can cause flu-like symptoms, such as nausea, dizziness, and fatigue, and if left exposed, it can be fatal. Certain types of mold can cause everything from irritation and flu-like symptoms to central nervous system damage, cardiac problems, and lung infections.

To help prevent these health problems, make sure you have a working carbon monoxide detector and keep your HVAC system well serviced and free of moisture.

What Happens If I Don’t Change My Filter?

Furnace filters should be checked monthly and changed every three months for standard fiberglass filters. Failure to change the filter can reduce your home’s air quality and cause premature wear to your furnace and HVAC system. It can also reduce the efficiency of your furnace, increasing your heating costs.

Keep spare filters handy and schedule furnace maintenance at least once a year to avoid any additional problems.

Furnace Service & Repair in the Cincinnati Area

Have you noticed frequent clogged filters or black filters in your furnace? Call our team at Rick’s Heating & Cooling for help. We can determine the cause and recommend the best maintenance or repair solutions to avoid future problems.

We offer furnace repair and maintenance throughout the Cincinnati area, and with more than 35 years of experience, you can count on us for dependable service and professional results.

Call (513) 899-6005 or contact us online to schedule furnace maintenance or repairs anywhere in Cincinnati, OH, or the surrounding areas.