What is an Air Filter & How Does it Work?

August 7, 2023
What is an Air Filter & How Does it Work?

Air filters are typically made from spun fiberglass (the same thing that makes up your attic insulation) or pleated paper & framed with cardboard for stability and rigidity. They are inserted into a specific place within your return air duct (usually a large drop-down vent in your hallway or other places in your home). These air filters act as barriers to prevent contaminants from entering your HVAC system or circulating within the air. Most filters are designed to block out dust, dirt, pet hair, lint, mold, bacteria, and more. Air filters typically have a MERV (minimum efficiency reporting value) that determines the type and size of pollutants the filter will work against.

How regularly you should replace your air filters could depend on the following:

  • Air filter model
  • Total indoor air quality
  • Number of pets
  • Household size
  • Air pollution levels and construction around the residence

For basic 1"–3" air filters, manufacturers typically tell you to replace them every 30–60 days. If you suffer from light to moderate allergies, you could install a better air filter or replace them even more regularly.

Or, if you live a more rural spot or less occupied residence (like a vacation residence) and there are fewer cars around, yearly could be regular enough.

Here are averages that may help you know how regularly you should get a new air filter at your residence:

  • Vacation house or one occupant and no pets or allergies: every 6–12 months
  • Ordinary suburban home without pets: every 90 days
  • One dog or cat: every 60 days
  • More than one pet or if anyone has allergies: 20–45 days

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