How to Make a Home Air Filter

This simple air filter is constructed from a box fan and disposable furnace filter.

How to Make a Home Air Filter

The filters on your furnace and air conditioner will help pull some of the dust and pet hair out of the air, but even if they run full-time, their capacity is limited. By making a second, independent air filter, you can increase the amount of filtered air in your home. .

Using small strips of duct tape, affix the filter to the intake side of the fan.

Turn the fan on to its lowest setting.

Place the fan in a bedroom, to help you breathe easier while you sleep; in a basement, to filter out mold spores that can cause allergies; or in an open window (facing inward).

Things You Will Need

  • 20-inch box fan with variable speeds
  • 20-by-20 inch furnace filter
  • Duct tape


  • Furnace filters made of white, accordion-pleated material and marked "HEPA" are very effective and cost about $7 each, or less if purchased in multi-packs.
  • Change the furnace filter once every month. In a very dusty environment, you might want to change the filter more often.
  • Run the home air filter in a bedroom for a couple of hours before bedtime to help clean the air.


  • Monitor the air filter during its first few hours of operation, to be sure the motor doesn't overheat.
  • If the fan overheats or begins to slow down, pull the plug and install a fresh furnace filter, or purchase a better-quality fan.
  • Turn off the fan before leaving the house.