What Can A Dirty Air Filter Do To My HVAC System?

Posted on: 23 July 2015


Your air filter is primarily responsible for cleaning the air your HVAC system sucks in of dirt, dust and other particles. Depending on how frequently you use your air conditioner and heater, this filter should be replaced every one to three months. Replacing your air filter is important for more than just keeping your indoor air clean, however. Going too long without replacing your filter could cause damage to your system and even shorten its life.

Ineffective Air Filtering

If your air filter becomes coated with dirt and dust, eventually excess dirt will start to flake off and enter your ducts. Essentially, if your air filter gets too dirty, everything past the air filter will get dirty, too.

This can eventually present minor health problems for anyone living in the house, because having dirt, dust and allergens concentrated into your ducts and then blown around is worse than having them rest on the floor or drift around. If you have allergy problems, a dirty air filter will eventually do absolutely nothing to help them.

Inefficient Cooling and Heating

A dirty air filter can reduce your system's efficiency by a noticeable amount, and this can reveal itself in two different ways.

  1. Your house doesn't get cool or warm as fast. A dirty air filter means reduced air flow, which means that less air will be moving through your ducts.
  2. You'll start receiving higher energy bills. The reduced flow of air means that it will take longer for your desired temperature to be reached. This is also because a dirty filter means your system needs to exert more effort to draw in air, and that can cause it to use more energy.

So not only will your house not get cool as quickly, but you'll pay more money than usual for that decreased efficiency.

Malfunctioning or Damaged System

There are a few ways that a dirty air filter can start to cause damage to your system.

  1. If your HVAC system isn't able to pull in enough air, the evaporator coils responsible for absorbing heat may get so cold they freeze over. This problem is twofold: frozen evaporator coils can cause your system to shut down or run completely ineffectively, and the melting ice can also cause water damage.
  2. A dirty air filter, in essence, suffocates your system. Think about how much more effort it takes to breathe if you put a cloth over your mouth. If your system can't pull in enough air, it may start to overheat. While this may not cause any problems immediately, it can place excess wear on your system's parts.

If you don't have any new filters, you can temporarily alleviate this problem by removing the filter completely. However, you should still replace the filter as soon as possible. If there is no filter, dirt can more easily get inside the evaporator coils, and this too can cause the coils to freeze.