Why Does My AC Filter Get Dirty So Quickly?

Why Does My AC Filter Get Dirty So Quickly?

According to most manufacturers’ instructions, it’s best to replace your air filter once a month. Otherwise, dust and debris will build up, create a clog, and restrict the airflow. If your HVAC system does not receive enough air to circulate, it will break down sooner or later.

However, if your AC filter is getting dirty too often and way before the end of the month, there may be a problem. This typically occurs due to an overheated HVAC system or contaminated air in your home. 

Before you call your HVAC technician, it’s best to figure out what’s causing this problem and how to prevent it in the future. Here are nine reasons your AC filter may be getting dirty too quickly.


If you have pets, your air filter will probably dirty way faster than usual. That’s because pets shed, regardless of how young and healthy they are. Not only will their fur cover every surface of your home, but it will also find its way inside the AC filter. 

Eventually, it will cover the air filter entirely and restrict airflow. That’s why pet owners need to replace their AC filters more often than usual – at least twice a month.

Read more : Best Air Filter for Home with Pets


If you have a large number of people living in your home, you’ll also need to change your air filters more often. This is crucial not just for the maintenance of your AC system but also for the health of your family members. 

If anyone in the house smokes, soot will gather in the AC filter much faster. Having unclean air is non-negotiable, especially if you live with anyone suffering from asthma. It may be better to invest in HEPA filters if you’re tired of changing your air filters too often. 

HEPA filters work better than most cheaper alternatives, catching even the finest dust particles and allergens. Of course, replacing HEPA filters once a month can be expensive, so it’s better to invest in washable HEPA filters.

You’ll only need to take them out and rinse them once a month. But make sure to let them dry overnight before putting them back, as wet air filters can cause various issues in the HVAC system. 


The quality of your AC filters could also be why they’re getting dirty too often. If you’re on a budget, it can be difficult to replace expensive AC filters every month. However, low-quality AC filters turn out to be more expensive in the long run since you’ll need to replace them way more often.

Plus, they may end up causing other issues within the HVAC system, which can cost hundreds of dollars to repair. It’s better to opt for high-quality air filters, which are a worthwhile investment. Make sure your air filter has a high MERV rating, with 20 being the highest.

Thermostat Fan

If a low-quality air filter isn’t the issue, take a look at the settings on your thermostat. The fan options have two settings: Auto and On. If your thermostat fan is set to Auto, it means it will turn on when your heater or AC turns on to regulate your home’s temperature. 

Then, after reaching the desired temperature, the fan will turn off along with the AC or heater. However, if the thermostat fan is set to On, it will constantly be running. This will cause your home’s air to circulate constantly through the AC, which makes the AC filter get dirty faster.


Your AC filter may be getting clogged with soot coming from various sources within your home, including candles, cigarettes, and furnaces. If no one in your home smokes, check for a blue frame in the furnace. 

If the flame is orange or yellow, there’s most likely an obstruction in your HVAC system. It’s best not to try this issue with yourself, as gas can be dangerous. Instead, call an HVAC technician to help you diagnose the issue.

If your furnace isn’t the problem, your candles may be. Look for petroleum jelly in the ingredients list, as these candles produce more soot than others. Other than that, candles with braided wicks may be more expensive, but they produce less soot.


Mold could also be the reason behind your AC filter getting dirty too soon but look for symptoms of mold growth first. That includes itchiness, watery eyes, water damage, musty smells, and condensation inside your windows. 

In the worst-case scenario, you may find mold growth in your home. Installing a humidistat can help you prevent this issue, but if it’s already too late, you’ll need to schedule a professional mold inspection. 


If your home’s ductwork has a leak, it can attract dust from unclean areas, such as a crawl space or your attic. As a result, your air filters get clogged quickly, especially if it’s placed near the AC’s inside unit. 

Aside from clogging up your AC filter, duct leaks can raise your electricity bills drastically. In fact, 20-30% of the air moving through the ductwork is due to duct leaks, which makes your HVAC system work harder and raises your utility bills.

If you suspect a duct leak, call your HVAC contractor to seal them.

Pleated Air Filter

If you have a one-inch pleated AC filter, it’s worth noting that they get dirty faster. That’s because they’re manufactured to trap more airborne contaminants, as they have a finer net. To fix this issue, you can simply switch to a more affordable and disposable fiberglass filter. 

Other than that, a thick pleated filter could work best too. But if you really want to improve the air quality in your home, an air cleaner would be the best investment.

Read More : Fiberglass vs Pleated Air Filters


The current weather can also influence the performance of your AC filter, especially if it’s too hot or too cold. Extreme weather conditions will cause more air to be pushed through the HVAC system with the help of the blower motor. 

Not only does this make the AC filter clog up faster, but it can also make your HVAC system work harder. As a result, your utility bills will be higher, and your AC system will face inevitable failure.


Now that you know what’s causing your AC filter to get dirty so quickly, you can prevent it in the future. If the problem persists, contact your HVAC technician to solve the issue.