Your air filter is black because of soot. This sounds scary, but, it's usually no big deal. The good news is that, if your filter is black with soot, it means it's doing its job. Better to have soot on your air filter than in your lungs, right?
For most homeowners, black air filters aren't a cause for panic. They simply mean that you need to increase the frequency that you change your air filters, and that the filter is doing its job.
Mold is a very concerning cause of black filters. The black appearance on filters can sometimes be black mold. This occurs when moisture from air conditioning condensation gets transferred to the air filter. Humid conditions and wet environments invite mold.
If you've checked your air filter to find it black instead of the usual layer of grey dirt and dust, that's not normal. So, what's causing this? Soot build-up, also called “black soot deposition”, is most likely the reason behind a black filter.
What has actually happened in your engine is the air filter has become dirty or clogged. This reduces the airflow, changing the air-fuel mixture. The rich fuel mixture creates a black soot residue which covers the spark plugs.
If the filter is newly installed or just recently changed, black particles may be noticed in the water. This is fine carbon particles left over from the manufacturing process. Flushing the system as outlined in the install instructions will eliminate this situation.
You can usually tell that the blackness in your air filter is mold because it'll be wet and slimy, rather than dry and powdery like soot. By the way, try not to touch the mold too much. It's not good for you.
Soot is one of the most common ways you can turn your air filter black. Most often, it is caused by candles or gas water heaters.
Soot particles released by wood fires or incomplete combustion of candle oils coalesce over time, forming black dust. It will continue to collect if surfaces aren't cleaned every day. The dust can accumulate on walls, windows, and cabinets as well as behind doors and in crevices if your home isn't well-ventilated.
Smoky quartz, a common mineral found in dirt throughout the US, can cause black specks in your sediment filter — it's normal.
Black particles from the HVAC system are typically mold, rust or insulation.
Use a soft-bristled brush or cloth to remove visible mold growth from the unit's interior. Wipe down the interior surfaces with a clean, damp cloth to remove any residual cleaning solution. Clean the air filter thoroughly with the same solution, then rinse it with clean water and allow it to air dry completely.
Brown. In most cases, the brown residue accumulating on your filter is from household dust, pet dander and other airborne particles.
The best way to know if the air filter needs replacement is via visual inspection. Locate the air filter housing (typically a rectangular box near the engine), open it, and look at it. The filter material should be almost white. If it's dirty, clogged, or covered in debris, it's time to replace it.
Since mold spores are usually about 1-20 microns, HEPA filters are perfect for extracting spores from the air. It's important to be aware, however, that even though HEPA air purifiers can efficiently filter mold spores out of the air, you need to remove the mold first if you have a mold problem in your home.
How Often Do I Need to Change Out My Air Filter? Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.
Its smell is often described as musty and earthy, similar to the scent of dirt or wet, rotting leaves. If you see black spots or black dust appearing around air vents, there's a good chance that mold is growing inside.
The presence of a large amount of soot around your furnace can indicate that your furnace is giving off carbon-monoxide due to partial combustion. If you have a carbon monoxide detector in your home, this might start going off to tell you – if you don't have one, it's a good idea that you do.
The most likely effect of exposure to carbon black is lung disease. Inhaling carbon black particles can irritate the lungs and cause coughing. Carbon black can also irritate the eyes, nose, and throat. When people are exposed to high levels of carbon black over many years, the particles may lodge deep in their lungs.
Pollutants in the air can cause a build-up, turning your filter black and making it less effective. The pollutants come from many sources, including exhaust fumes, cleaning chemicals, and even burning candles. When these pollutants settle on the filter, they can prevent air from flowing freely through the system.
Though the appearance of mold will vary depending on what type it is, it shouldn't be too hard to identify. Watch for green, yellow, black, or white stains developing on your AC system's walls and air filter that display a fuzzy, velvety texture.
In extreme cases, a dirty air filter may become so clogged that the filter itself becomes sucked into the system, compromising air flow through the filter. This situation poses a serious fire hazard and can cause extreme damage to your HVAC unit and your home.
A third possible cause is that the air conditioner might have mold growing inside it. An AC unit that has sat turned off for any amount of time in warm, humid conditions may very well have developed mold and mildew. As the AC is turned on, wet, black particles may blow out of the unit.
Simply mix one cup of white vinegar with a gallon of warm water and spray the solution on the mold. Give the solution time to work its magic (about an hour) and brush the remnants out of your air conditioner. However, since mold is toxic, you must wear protective gear while cleaning the mold out of your AC unit.
While it's very dark, it's not a single color, as the name implies. Instead, black mold is actually very dark green, brown, or black and is wet, shiny, and slimy. Black mold often looks fuzzy. It tends to form clusters of circular spots that may have fuzzy white edges and when wiped, leaves a green stain behind.