One easy and affordable way to make your own air cleaner at home is with a box fan and a furnace filter. These “filter fans” can filter out the small particles that are common in wildfire or wood smoke. Particle pollution can lead to a number of immediate and long-term health impacts such as trouble breathing, asthma attacks, and lung and heart disease. Particle pollution is especially dangerous for children, the elderly, and people with sensitive immune systems.

We have tested the performance of these filter fans and they dramatically reduce fine particles and black carbon from the air. See the graph below that shows an example of the filter fan performance.  

Supplies you need to make your own:

• 20" x 20" box fan
• 20" x 20" x 1" MERV 13 or FPR 10 filter 
• Power drill*
• 3/4" screws*
• 2" corner brackets*

* If you do not have access to a power drill, you can simply use any kind of tape or a bungee cord instead of screws and brackets.

All supplies can be found at home improvement or hardware stores.

See the video tutorial on how to build a filter fan yourself:

The video was made possible by the students from RecTech, an internship program with Seattle Parks and Recreation. RecTech’s mission is to remove barriers and train students through technology to better prepare them for college. 

Important Tips While Installing Filter to the Fan: 

• Make sure the filter is placed against the back of the fan.
• Make sure the arrows on the filter point towards the front of the fan or follow the same air flow of the fan.

Important Tips While Using Fan:  

Testing by UL found no safety concerns with filter fans. Even so, it is important to follow these instructions:

• Follow the box fan manufacturer’s instructions, which can include: Don't leave children unattended when the fan is in use, don't use an extension cord, don’t use near water, and don't use a damaged or malfunctioning fan.
• If you are using your own fan, make sure it is 2012 or newer.  Older models pose a fire risk and should not be used.
• Use the filter fan in the room you spend the most time in.
• Position the filter fan toward the middle of the room, away from walls, drapes, and dusty spaces.
• Close all windows and doors while filter fan is in use. The filter fan won’t be as effective if pollution from outside is coming into the room. However, if it is too hot inside, you can open a window.
• Running the filter fan in a window will result in reduced filtration and make the filter get dirty faster.
• It takes at least 10-15 minutes to clean a small room (15’x15’).
• The filter fan cannot clean an entire large room. If you are in a large room, place the filter fan near you so that it keeps the air around you clean.
• Replace filters after 3 months of use or when they look dirty.
• Filters should have a “MERV-rating” of 13.

You can also download our fact sheet and assembly instructions below.