Do masks protect you from wildfire smoke? We asked experts.

Noxious smoke from several wildfires in Northern California and Oregon was carried by winds into the San Francisco Bay Area on Tuesday, leaving many of us wondering how to protect ourselves from whatever toxic particles may be lingering in the air. Unfortunately, the cloth mask you usually wear inside the grocery store is effectively useless, according to experts. 

“These wildfires have generated a large smoke plume covering the entire Bay Area,” wrote the Bay Area Air Quality Management District in a Sept. 20 news release. “Air quality has degraded to mostly ‘unhealthy for sensitive groups’ and ‘unhealthy’ Air Quality Index levels in most of the Bay Area.” As a result, the district issued a Spare the Air alert through Thursday, Sept. 21, and forecasters with the National Weather Service’s Bay Area office predict that the haze will linger until at least Friday. 

Wildfire smoke can cause a wide array of health issues, according to the district. Along with eye and throat irritation, it can cause coughing and wheezing, especially among people with asthma, emphysema and chronic obstructive pulmonary disease, or COPD. The potent mixture of air pollutants can be especially harmful to sensitive groups: children, the elderly, pregnant people, and people with heart and respiratory conditions, the California Air Resources Board wrote.

Experts say that to truly protect yourself, you need to wear an N95. 

“If folks have to go outside, the only mask that really protects you from this really fine particulate matter is an N95 mask,” Tina Landis, a public information officer with the district, told SFGATE. It also needs to be properly fitted to work. Because the masks don’t come in youth sizes, she recommends that children stay indoors completely, if possible. Bandanas and surgical masks are equally ineffective, she said, and fine particles will pass right through them. 

“There’s no advantage to surgical masks in wildfire smoke,” agreed Dr. Monica Gandhi, a professor of medicine and infectious diseases doctor at UC San Francisco. 

But overall, the best method for avoiding smoke, according to Landis, is to stay indoors, run an air purifier, and firmly shut doors and windows. “If you’re being exposed for days or weeks upon any one period, you know, that does have an impact on your lung function,” she said. “The short-term impacts as well as long-term.”