If the filter is still in good condition, light should shine through. If the filter is dirty or clogged with debris, the light will be obstructed, indicating it's time for a replacement. The presence of visible mold is another one of the dirty HVAC filter symptoms that indicates it's time for a replacement.
Dirty Air Filter
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.
A dirty air filter is gross – often coated in gray or tan filth that may flake or fall off when disturbed. If it looks like this, it's time to replace your filter.
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.
Contaminants in the Air: High levels of dust and debris put a strain on your unit, making your filters clog faster. An increase in the number of people in your home can also increase the amount of dirt being kicked up into your system.
When you leave an AC unit's air filter clogged for too long, you can experience a failure of the entire system. This is because the unit can only work for so long at twice the power before it finally breaks down.
Filters with a MERV rating of 1 to 7 typically cost between $5 and $20. Filters with ratings of 8 to 13 can cost anywhere from $20 to $150. HVAC systems in residential homes usually don't need (and often cannot handle) filters with a MERV rating of more than 13.
They can make your family sick:
Your family may suffer upper respiratory infections if they experience coughing, headaches, sneezing, nasal congestion, sore throats, runny noses, and low fevers due to dirty air-conditioning filters.
The filter looks dirty: This is simple but effective – look at your air filter. If it looks dirty, dusty, or has clumps of hair and dust, it's time to change it.
Black Soot Deposition
Black soot can quickly turn our air filters black. This is usually a result of burning candles. Candles are made of carbon-based materials that don't all combust when burned. They end up producing tiny soot particles which then get into our carpet, on our furniture, and in our air filters.
No, you should never run your AC without a filter!
While your HVAC unit will run, it should never run without an air filter. Dirt is the number one cause of air conditioners breaking down, so running your unit without an installed air filters can cause serious damage.
With that said, how dirty should an air filter look? A dirty engine air filter will be either completely dark brown or black. If this is the case, it's time to install a replacement.
First, check your filters and coils for dirt and debris that may be impeding airflow. Once you've cleaned the filters and coils, run the air conditioner with just the fan so that the ice accumulation can melt off. If the AC still doesn't blow cold air, it could be that refrigerant levels are too low.
If you don't change your air filter, it can quickly become clogged with dust and debris, preventing proper air filtration. This leads to a variety of issues for your HVAC system including system inefficiency, higher energy bills, inadequate air quality, and ultimately failure.
It's gray or brown instead of its original white or light color. You'll notice a thick layer of dust, dirt, and debris covering the filter's surface. The filter may look clogged or matted, with visible clumps of dust and hair.
Air duct cleaning costs $388 on average, but ranges between $150 and $800, depending on your region, the size and type of ductwork, and the number of vents. Air duct cleaning costs $388 on average, but can range between $150 and $800.
What happens if your HVAC filter is dirty? A dirty HVAC filter restricts airflow, which can lead to poor system efficiency, increased energy costs, and wear and tear on the unit.
The short answer: You can get away with running your AC without a filter for a short period of time. However, doing so for longer than 6-8 hours can hurt your system and decrease your home's indoor air quality.
Most manufacturers recommend changing basic fiberglass filters every 30 days. Higher-quality pleated filters should generally be changed every 90 days, though they can potentially last up to six months.
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. A moldy air filter is usually caused by a problem with the condensation drainage in your AC system.
Clogs May Cause the Furnace to Shut Down
In the most severe cases, a dirty furnace air filter may cause damage to the internal components of the furnace. If the furnace isn't able to turn on, this is an indicator of damage to the fan, pilot light, heat exchanger, pressure switches, gas valves, or other components.