Experts advise steps to keep indoor air clean during wildfire smoke

Health officials are urging residents affected by wildfire smoke to stay indoors and take measures to improve indoor air quality. Central air-conditioning systems should have filters replaced on schedule, preferably with MERV 13 or higher ratings, and be set to recirculate while keeping exterior vents closed. The University of Oregon’s Center for Wildfire Smoke Research and Practice advises running the system’s fan continuously throughout a smoke event.

Portable air cleaners should be HEPA-rated and free of ozone-generating technology. If only one unit is affordable, it can be used to create a “clean room” for prolonged occupancy. > "The basic message is that something is better than nothing," said Amy Kalkbrenner, an environmental epidemiologist at the University of Wisconsin-Milwaukee.

DIY box-fan filters, made by attaching furnace filters rated MERV 13 or higher to a box fan with duct tape, have been shown by the Environmental Protection Agency to remove fine particles as effectively as small commercial purifiers. > "The good news is they really work," Kalkbrenner added.

Window units, mini-split systems and portable air conditioners often lack adequate filtration. Researchers recommend sealing the unit in the window frame, setting it to recirculate, and pairing it with an air purifier or DIY filter. > "When smoke and heat occur together, the impacts on your health are even greater than when they occur by themselves," said Jess Downey, a researcher at the University of Oregon.

Homeowners should seal gaps around doors, windows and other openings with towels, tape or other material to limit smoke infiltration. > "Any areas in which air can come in, consider sealing up those areas to reduce the amount that’s coming into the home," said Dr. Khalilah Gates, a pulmonologist with Northwestern Medicine.

During high smoke levels, burning candles, fireplaces or gas stoves should be avoided, and people experiencing symptoms such as shortness of breath, chest tightness, headaches or eye irritation are advised to move indoors. Severe respiratory distress warrants immediate medical attention.