The Environmental Protection Agency recommends using a DIY box-fan air cleaner to combat wildfire smoke in several U.S. states.
The Environmental Protection Agency suggests that residents can create an affordable, effective air cleaner using a box fan, a MERV 13 filter, cardboard, and duct tape. This do-it-yourself solution serves as a practical alternative for those facing sold-out commercial purifiers as wildfire smoke continues to impact the western United States. The agency recommends using a 20-by-20-inch box fan manufactured in 2012 or later. By attaching a MERV 13 filter to the back and a cardboard shroud to the front, the cleaner can increase the clean-air delivery rate by 40%. The EPA notes that MERV 13 filters are particularly effective at capturing the small particles found in wildfire smoke. While these DIY units help create cleaner indoor environments, the Environmental Protection Agency warns that they are not a total substitute for following official evacuation orders. Residents are advised to check filters daily and replace them once they turn dark gray or brown.