How can we protect ourselves from wildfire smoke?

(1) Getting out of the smoke

One of the best ways to protect yourself from wildfire smoke is by going indoors. But, be careful that you are not just trapping yourself with smoke indoors too! Consensus advice includes:

• Closing your doors & windows to make it more difficult for smoke to enter.

• Turning off exhaust fans, like in the bathroom. If this air is being sucked out, it's likely that (smokey) air might leak in from elsewhere.

• If you have central heating/air conditioning and have at least a MERV-13 filter in your system, switch it to "fan" mode. "Fan" mode will move air through the filter continually, with the filter working to remove particulate matter from the air.

• Use air purifiers, whether commercial options or do-it-yourself Corsi Rosenthal boxes. These will help to remove smokey, polluted air that is already indoors.

(2) Reducing exposure if you must be outside

Realistically, it might not be possible or desirable to stay inside 24/7 during a wildfire smoke event. Sometimes, people are forced to be outside, whether for work (e.g., delivery workers, agricultural workers, construction workers, etc), commuting (e.g., going shopping, going to work, etc), or even just for mental health or balance. If you do need to - or decide to - be outside, it's valuable and important to take steps to reduce the harm that can be caused to you by smoke.

Over the past several years, there's been significant evidence accumulating that masks - especially high quality N95 or P100 respirators - can offer significant protection compared to not wearing anything. If you need to be outside during smoke, the evidence suggests that well-fit, good quality masks and respirators can help reduce the harm you experience from wildfire smoke.

Some evidence shows that the materials in masks are likely to help filter harmful components of fire smoke:

• Wagner et al 2022 modelled the effect of different filtration materials, which suggested N95 respirators offer the most protection, surgical masks offer some protection, cloth masks offer modest protection, and no mask offers (unsurprisingly) no protection.

• Garg et al 2023 actually tested different materials, showing very, very high filtration from N95 and P100 respirators, as well as significant protection from surgical masks, but limited filtration by the materials in bandanas.

Of course, it's not just the materials... fit also matters. If smokey air leaks around the mask, it's not going through the filter, so you're not being protected. Fortunately, other studies have examined effectiveness of different kinds of masks in real-world settings:

• Cherry et al 2022 examined the use of N95 respirators by wildland firefighters. Even though they only used them sporadically, those who occasionally used N95s suffered from fewer smoke-related symptoms than those who went unmasked.

• Hadley et al 2022 reviewed relevant literature and suggested N95 respirators can "effectively reduce PM2.5 exposure" in wildfire events, with surgical masks offering moderate protection.

• Holm et al 2021 conducted a review that found the use of N95 respirators could reduce children's wildfire smoke exposure by 80-95%, compared to 20% reductions in smoke exposure from surgical masks.

• There have even been blinded studies using 'sham' masks to examine the effectiveness of masks. Guan et al 2018, for example, did this in the context of air pollution, finding N95 respirators did indeed reduce adverse impacts from pollutants.

Finally, other evidence suggests masks can help reduce the burden of fire smoke on populations and healthcare systems:

• Kodros et al 2021 modelled the effect of masks & respirators on hospitalizations following their own tests of mask material effectiveness, finding that N95 respirators - and, to a lesser extent, surgical masks - can significantly reduce hospitalization.