How to Make a DIY Air Purifier During Wildfire Season

Clear the Air: For many of us, wildfire smoke is becoming a fact of life, and it’s not just an outdoor problem. Fine particulate matter can seep inside through doors, windows, and ventilation systems, where it can irritate your lungs and increase the risk of respiratory problems. During major wildfire events, like those going on in Colorado, Oregon, and Canada this year, portable air purifiers tend to sell out quickly. If you weren’t able to snag one in time, there’s a surprisingly effective backup.

How to Do It: Build a DIY air purifier by attaching a 20-inch MERV 13 furnace filter to the back of a standard 20-inch box fan, making sure the arrows on the filter point toward the fan. (The MERV rating is important: the higher the rating, the more protection they offer, so opt for a filter rated 13 or higher). Seal the edges with duct tape to reduce air leaks, then run the fan in the room where you spend the most time. For safety, use a newer fan manufactured after 2012 with a fused plug to reduce fire risk. Also, be sure the motor is clean, and never leave it running unattended.

The Benefits: Research from the EPA has found that DIY box fan filters can substantially reduce indoor smoke particles, so they can improve your indoor air quality in a pinch. Plus, they’re inexpensive and easy to assemble.