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Box Fan Filter Instructions

filter fan project video still

Why Filter the Air?

ScienceWorks is located in Oregon, where we are having some wildfires right now. There is quite a bit of smoke, dust, and soot in the air. Due to the high levels of particulates (small pieces of solids in the atmosphere) outdoors, most people are trying to stay inside. Breathing too many particulates can result in health problems. But even indoors, there can be unhealthy air due to smoke that comes in through gaps around doors and windows.
filter fan project materials
We are building a simple home filter system that you can make with a few materials that you might already have at home. The idea behind this design is to use a fan to pull dirty air through a filter, resulting in cleaner air coming out the other side. While this system may not clean the air as well as a commercial filtration system, it could provide some relief by removing particles from the air in the home.


  • Box fan
  • Two air filters (the kind you use for a home furnace)
  • Duct tape
  • Scissors or box cutter
  • Cardboard
  • Straightedge (optional)
  • Marker or pen

Watch the video for the step-by-step instructions. It works best if your box fan and filters are approximately the same size. For a 20 inch box fan, try using two 20x20x1 inch filters. That will make it easier to close the gaps with cardboard and tape. The important thing is to make sure all of the air being pulled into the fan passes through the filters, so be sure to tape the gaps. Otherwise, dirty air will bypass the filter and sneak through the fan, making the system less effective.