What Causes Home Air Filters to Turn Black?

Soot is one of the most common causes of black air filters. It is a by-product of burning candles, gas water heaters, and other sources of combustion. Carbon monoxide is another potential culprit, as it can leave a soot-like appearance on the filter when it leaks into the home. Mold can also form on the filter due to condensation on the evaporator coil, especially in humid conditions.

Regular maintenance and cleaning can help prevent these issues from occurring. When you notice that your air filter has turned black, the first thing you should do is check for soot and mold. If you don't find either, try to refrain from using candles and increase the number of times you dust. We recommend checking the air filter every 30 days and replacing or cleaning it if necessary.

You should not go more than 3 months without changing the air filter. Scented candles are often responsible for black soot deposition because they contain more “impurities” that don't burn properly. Look for candles with braided wicks, as they produce less soot. Avoid candles with petroleum jelly as one of their ingredients.

An activated carbon air purifier can also help remove soot particles from your home air. If you have a gas oven, check the color of the flame. If it's blue, everything works properly. If it is yellow or orange, the HVAC system is likely to be clogged.

Fireplaces can also cause black soot deposition if they are used during cold weather. High-quality air filters that are regularly replaced will keep soot trapped and prevent your system from deteriorating due to increased air tension that cannot easily pass through the filter. The price of air filters can vary widely, depending on their materials, the MERV rating (minimum efficiency report value), and whether they are washable.