How to Make an A/C Vent Filter

Air conditioning in a house is essentially a closed system.
The unit sends cooled air throughout the house with a system of ducts and vents or outlets in various rooms. It collects that air once it has passed through the house with a system of return vents and ducts, which gathers the "used" air at some central location and sends it back to the unit, to be cooled again and redistributed. The return air must be filtered to remove dust and debris before it re-enters the unit. Cooled air also can be filtered as it is distributed through outlets.

Step 1

Install an air conditioning return filter at some central location, like a hallway, where air flows naturally through a house. Place a return for air conditioning only near a ceiling, to collect air that has warmed as it passes through the house; combination heating/cooling returns normally are located at floor level.

Step 2

Fasten a metal return filer frame to studs or ceiling joists, depending on location. Fit the frame to the size of return required for air flow; you may have to cut into studs for very large returns, but these openings generally are framed during construction of the house.

Step 3

Size the return and filter to the output or air flow from the air conditioner; systems must be balanced so a return will collect all the air being put out, but not pull out too much to reduce the efficiency of cooling. Use removable return filters; there are many styles, most with paper or fiberglass elements which trap dust and dirt particles.

Step 4

Add filters in each vent or outlet, in the floor, on a wall or in a ceiling. Buy filters to fit the size of the vents or get material, typically polyester or similar foam, that comes in rolls or strips and can be cut to fit any vent. Remove vent covers; lift them out of the floor or unscrew them from a wall or ceiling mount. Fit the filter material inside the vent cover and replace it.

Step 5

Use an electronic air filter in extreme cases. Mount these mechanical devices in the return air frame, with an air flow sensor that will activate them only when the unit blower is turned on. Use these either in wall or ceiling return entries with access to electricity to power the filter.

Things You Will Need

  • Air return grill
  • Outlet covers
  • Polyester foam or similar filter material
  • Electronic filer (optional)

About the Author

Bob Haring has been a news writer and editor for more than 50 years, mostly with the Associated Press and then as executive editor of the Tulsa, Okla. "World." Since retiring he has written freelance stories and a weekly computer security column. Haring holds a Bachelor of Journalism from the University of Missouri.