Project Guide

How to Change a Home Air Filter

Maintenance Hints
A washable air filter.
  • Find your air filter location. You may have more than one air filter in the home to service. The return air register, the air handler cabinet and even a window AC unit will all have an air filter that requires replacement or cleaning.
  • Get the correct size. Disposable air filters usually come surrounded by a cardboard frame, while reusable washable air filters have a plastic frame; either will indicates the specific size of the filter. When you search for a replacement, choose the same size. For filters that don’t indicate size, use a measuring tape to measure the length, width and thickness of the filter. Use these numbers to select a new filter. 
  • Place the filter correctly. Most filters are printed with an arrow that indicates furnace filter air flow. Place the filter with an arrow pointing toward the furnace, in the direction of air flow. Correct placement is important. The unit will use more energy if the filter is not properly installed; it has to work harder to pull air through the opposing side.
  • Check air filters monthly. Replace or clean as needed and be sure you properly install your replacement filters. Dirty air filters make the unit work harder and impact your indoor air quality; the same is true if air filter is backwards.
Replace Air Filter in Return Air Duct
A person removing an air filter from a wall vent.
  • Unhook the latch on the cover grille.
  • Wipe the grille clean with a microfiber cloth. If dust has built up between the slats, wrap the tip of a flat screwdriver with a microfiber cloth and use it to gently clean in between the slats or vacuum the cover with a brush attachment.
  • Insert a new filter, ensuring the correct furnace filter direction.
  • Close the cover grille and secure the latch.
Replace Air Filter in Air Handler Cabinet
A person vacuuming the grille cover on an air vent.
  • Turn off the power to the HVAC unit. If you are unsure how to turn off the furnace, consult your unit's manual. Do not run furnace without a filter in place.
  • Remove or unlatch the door and clean as indicated above.
  • Check the filter type. If it is disposable, replace with a new filter in the correct size.
  • If the filter is reusable, first brush it to remove surface dirt, then run a vacuum with a soft brush attachment over the face to pull out more imbedded dust and dirt.
  • Run water through the filter in the opposite direction of air flow; you can use a low-pressure spray to assist in the cleaning.
  • Allow the reusable filter to thoroughly air dry before you replace it.
  • Do not resume power to the HVAC unit until the clean, dry filter is in place.
Replace Air Filter in Window AC Unit
A person unplugging a window AC unit.
  • Turn off the AC and unplug the unit.
  • Remove the front cover; if needed, clean as indicated above.
  • Remove the filter and shake vigorously outside to dislodge as much dust and dirt as possible.
  • Rinse the filter lightly with soapy water, then rinse with clear water until clean.
  • Scrub the cover in the soapy water, rinse and dry with a microfiber cloth.
  • Air dry the filter thoroughly before replacing it in the unit.
  • Replace the filter, lining up the notches on the filter frame with the spaces inside the filter compartment.
  • Replace the cover and restore power to the unit.

Common Types of Air Filters
Two carbon air filters.
  • Ordinary furnace filters are inexpensive, but only provide minimal benefits.
  • Pleated air filters are typically more eco-friendly and greatly improve indoor air quality for those with allergen sensitivities. They are a bit more expensive than the standard air filter.
  • Carbon air filters are good at clearing odors, chemicals and smoke from the indoor air. This is due to the chemical bond the carbon will create from the pollutants as they pass through. However, they are not enough to purify the air on their own as they will not trap allergens or microorganisms.


Tip: Learn more about selecting the right filter with our air filters buying guide.

Read our guides on how often to change air filters and how to clean an air conditioner filter for more ways to take care or your indoor air. 

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