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A furnace filter is an inexpensive but crucial component that keeps your heating system free of dust and other particles. It traps a substantial amount of debris and will certainly change colors over time. That said, if you’ve ever gone to change it and noticed it was completely black, it can be quite the shock. You may wonder whether that’s normal, and the answer is no. Let’s have a look at what could cause it.
Are There Filters That Come Black in Color?
The vast majority of furnace filters on the market have a white color. This makes it easy to see when they are clogged and need to be replaced. There are exceptions, including filters that are orange, yellow, green and blue. There are even filters that change color over time as an indicator. Black is unusual with a notable exception: pleated filters that the manufacturer has coated or impregnated with activated charcoal. This helps reduce odors in the air moved throughout the home. Still, even with activated charcoal, you should be able to discern the difference between it and a black foreign substance.
Carbon Monoxide
Furnaces that burn natural gas, propane and heating oil produce carbon monoxide (CO) as a byproduct. CO is a gas that you can’t see, smell or taste. At high enough concentrations, it causes CO poisoning. Early symptoms can include headaches and dizziness, but it can eventually cause death.
When a furnace is well-functioning, it keeps the CO separate from the air you breathe. It then exhausts the gas out of your home where it mixes with the ambient air. If the CO is leaching into your air, it will leave behind a black residue as it passes through the furnace filter. It’s important to note that your furnace isn’t the only system in your home that can cause this. Any fuel-burning appliance can. That includes water heaters, fireplaces, dryers, stoves and so forth.
Solution
Cease using any fuel-burning appliances right away. Contact a company like ours that has both technicians and plumbers who can inspect your gas lines and all appliances. The CO levels don’t have to be high to blacken your filters, but they can elevate quickly and become dangerous.
You should have adequate coverage from CO detectors in your home. If you do and they fail to activate, replace them immediately. It’s also paramount that you schedule an annual inspection and cleaning of your furnace and other fuel-burning appliances in your home.
Soot
Soot is black particulate matter and the result of incomplete combustion. If your furnace or other fuel-burning appliances have a combustion problem, they can give off soot. With soot in the air, a fresh furnace filter can turn black quickly. Homes with traditional fireplaces and wood stoves will often have soot in the air. You can also generate a surprising amount of soot by burning candles.
Brief exposure to soot isn’t generally cause for concern. If your furnace filters are black, though, it is a serious cause for concern. You’re breathing the soot in, and it contains ultrafine particles that can lead to serious diseases with long-term exposure. Even at relatively low levels, it can be a notable trigger for people with asthma, severe allergies and other respiratory conditions.
Solution
Schedule an inspection and cleaning of all your fuel-burning appliances to rule them out. Keep an eye on your pilot lights, which should be blue and never yellow or another color. If you burn wood in the home, ensure that it’s dry. Moist wood will cause soot. Have your fireplace and chimney professionally cleaned once a year. Take care with the candles you burn. Soy wax candles, for instance, don’t produce soot in the manner paraffin wax candles do. Swap out your furnace filter more frequently for a while. As you gain control of the situation, doing so will help you monitor your progress.
Mold
The presence of mold in your home can cause your furnace filters to turn black. There’s a widespread misconception that black mold is inherently more dangerous. All mold is bad for your health with enough exposure. Black mold can produce mycotoxins that make it toxic. Not all black mold does, and some green and other colored molds can produce it as well. In addition, the black color doesn’t necessarily mean black mold. It could be mold dying on the filter along with other biological growth.
Solution
You should schedule an inspection and cleaning of your entire HVAC system. Our technician will ensure that there’s no excess moisture because of a condensate drain line blockage or other issue. You may also want to schedule a video camera inspection of your ducts. This is to rule out mold in the ductwork.
Mold on your furnace filter doesn’t necessarily suggest that the problem originates with your furnace. With a buildup on your filter, you probably have an infestation, but it could be in a bathroom, basement, crawl space and so on. Consider scheduling a mold inspection for your entire home.
Clogged Filter
If you’ve ruled out CO, soot and mold, it may just be a clogged filter. Filters will typically turn shades of gray as they fill up with dust, dirt and other particles. Still, if the dirt is of a darker color, it will make the filter black. This can be common in communities with nearby farms that grow crops. The rich soil particles get into the air, and your furnace filter will eventually trap them and turn darker.
Solution
Swap your filter out, and monitor the new one. It may only be a seasonal or an occasional problem. If you’re worried about the soil and other particles in your air, consider a whole-house air purifier. An air purifier that provides four or more air changes per hour will easily control the issue for you.
Poor Ventilation
Ventilation systems are an uncommon but potential cause of this problem. Improper ventilation can lead to the various ducts and lines overheating. That can cause cork tape and other materials to melt and give off particles that the filter traps. The materials used for HVAC are generally not hazardous.
Solution
If you suspect this is your problem, schedule an inspection of your entire ventilation system. Your technician may notice the problem during a furnace tune-up or duct inspection but not necessarily. It’s a good idea to have your ventilation system inspected every three to five years regardless.
Are You Experiencing Black Furnace Filters in Fox Valley?
If you live in Fox Valley or a surrounding area and are experiencing black furnace filters, Black-Haak can help. Our HVAC technicians also install and service furnaces, boilers, air-source and geothermal heat pumps, air conditioners and ductless mini-splits. We specialize in indoor air quality, including whole-home air purification systems, dehumidifiers and humidifiers. Our team installs programmable and smart thermostats and all other smart home automation devices. We have licensed electricians who wire and rewire and perform inspections, repairs and installations. Those services extend to electrical panels, indoor and outdoor lighting, surge protection, ceiling fans and EV chargers. We have plumbers, too. They specialize in drain cleaning, leak repair, fixtures, sump pumps, garbage disposals, tank and tankless water heaters and much more. Call today to request service or to ask questions about the products and services we offer.
