Your distance from a wildfire doesn’t just determine how safe you are. It also determines what you’re most at risk of.
Presuming you’re out of immediate physical danger, your short-range risk will come from large particles, released into the air as the fire burns through material, and noxious gases like sulfur and nitrogen dioxide, which inflame the respiratory system and make it difficult to breathe.
“As you get a little further away, we worry about particulates, which are [about] a sixtieth of the size of a human hair,” says Brian Christman, a professor of medicine at Vanderbilt University and spokesperson for the American Lung Association.
Christman explained that these tiny particulates – the scientific community calls them PM2.5 – are so small that, when breathed into the lungs, they can cross the blood-air barrier and circulate in the bloodstream, increasing the risk of heart attacks.
That’s just one of the potential health consequences of inhaling wildfire smoke.
A recent study found that children exposed to high levels of PM2.5 experienced fundamental changes to their immune systems, making it more likely that they’d develop allergies or infections. Another suggested that exposure to wildfire smoke can affect a newborn’s birth weight. And wildfires are known to increase respiratory-related hospitalizations and even deaths.
But the effects of wildfire smoke aren’t fully known yet. “There hasn’t been a focus on wildfires until the past few years, when they’ve really increased with climate change,” said Mary Prunicki, the director of Air Pollution and Health Research at Stanford University’s Sean N. Parker Center for Allergy research. “I don’t think it’s been on a lot of people’s radar.”
Complicating matters, Prunicki said, is the fact that “wildfire smoke” can vary. A forest fire burns different compounds from a fire that’s making its way through a town. Neither, however, is good for your health.
Enter the N95 mask. Properly fitted, the mask is designed to filter out 95% of particles larger than 0.3 microns across. “It’s fairly effective in reducing exposure to the high-level particulates you see in these circumstances,” Christman said.
And for many dealing with a fire in the near – or even not-so-near – vicinity, it’s a great first line of defense. “Particles can travel hundreds of miles,” said Kent Pinkerton, a professor of pediatrics at UC Davis who studies the effects of pollutants on the respiratory system.
During the Camp Fire, he explained, the highest concentrations of smoke were actually found in the Bay Area, about three hours away. “Those kinds of situations are something that is hard to control for,” he said.
Those are precisely the kind of situations – when you’ll be exposed to particles in the air but have to be outside some of the time – in which experts recommend using the N95.
Not everyone agrees. During the Camp Fire last year, Sacramento County’s Department of Health Services recommended N95 masks only for those actually in a fire zone. Because the mask restricts the flow of air –the unfortunate consequence of breathing through a filter, Pinkerton said – the county’s public health officer deemed it dangerous for people with heart or respiratory conditions.
In addition, the Department of Health Services pointed out that the presence of an N95 mask might “encourage outdoor activity which could worsen exposure” – in effect, that it would create a false sense of security.
There are other limitations. To work properly, an N95 mask has to be properly fitted to your face so that a seal is created around the edges, and a regular-sized mask won’t fit a child or anyone with a beard.
And while the mask is designed to filter even tiny particles, it won’t work at all on toxic gases – which means it’s not an effective tool for anyone up close to a fire.
Christman cautioned that even the way you breathe can affect how effective the mask is. “If you’re breathing more normally, you have more of a circuitous pathway to your mouth and nose,” he said. If you’re exerting yourself or otherwise breathing quickly, you’re more likely to pull air from around the mask.
The N95 doesn’t just protect against wildfire smoke. Medical professionals use the masks to prevent the transmission of infectious diseases, as do people whose work exposes them to tiny particles (think construction workers and cabinet makers).
Most of the evidence that the masks work come from these other uses, not from wildfires. “It makes sense that it obviously would help during wildfire smoke exposure, but there’s not a lot of [scientific] literature regarding the improved health outcomes from wearing the masks,” Prunicki said.
The best approach
Yet the research does suggest that for small particles – precisely the kind that are most dangerous to people a short distance away from a wildfire – the mask is a valuable defense tool. “That’s the reason it has been recommended for many different conditions when air quality may not be so good,” Pinkerton said.
In short, whether you’re waiting to be evacuated or just need to walk around in an area with poor air quality, the N95 is your friend. Make sure it’s formed a seal around your face, and breathe normally for maximum protection.
However, cautions Janice Nolan, a spokesperson for the American Lung Association, the N95 doesn’t give you a free pass to walk around in unsafe air. It’s important to get inside – preferably somewhere with recirculated air and a filter – as quickly as possible. It’s also a good idea to use towels around the cracks of doors and windows to keep particles from getting into the building.
“Don’t treat a day when you have poor air quality as though you could do anything you want,” Pinkerton said.