Is It Safe to Go Outside Today? A Smoke-Day Decision Guide

Short answer: check the number for your city, not the sky. Wildfire smoke can look apocalyptic and register as "Moderate," or look like an ordinary hazy afternoon and actually be "Unhealthy." Once you know the real AQI, the decision gets simple — and it depends less on how bad the air is overall and more on what you're about to go do in it. A short walk and a hard run are not the same exposure, even in identical air.

What AQI level is actually safe to be outside in?

Under 50 ("Good"), there's no adjustment to make — run your errands, let the kids play, open the windows. Between 51 and 100 ("Moderate"), the air is fine for almost everyone, though a small number of people who are unusually sensitive to smoke may notice mild symptoms. It's once you cross 100 that the calculus starts to shift, and it keeps shifting as the number climbs.

Those five bands are the standard for talking about air quality across Canada and the US, and they're what your city's live reading gets sorted into. The catch is that a single "AQI for your city" number often comes from a monitor miles away — smoke is patchy. It can be 60 downtown and 140 near a valley ten minutes away. That's the whole case for checking a live, local reading instead of eyeballing the horizon.

Does "safe" depend on what you're doing outside?

Yes — more than it depends on the AQI number by itself. A quick trip to get the mail and a two-hour bike ride move very different amounts of smoke into your lungs, even in identical air. The table below is a rough decision guide by activity: go means proceed as normal, modify means shorten it, shift the timing, or add a mask, and stay in means skip it if you have the option.

Those calls are for the general population. If you're pregnant, over 65, have asthma, COPD, or heart disease — or you're deciding for a kid — shift everything one column left. Treat "Moderate" like "Sensitive groups." Treat "Sensitive groups" like "Unhealthy." The AQI scale was built with a buffer for the general population; it wasn't built with much of one for lungs and hearts that are already working harder than average.

If your job or commute means staying in just isn't an option, a properly fitted respirator meaningfully cuts your dose — a cloth or surgical mask does almost nothing against wildfire smoke. See which mask actually filters PM2.5 before you rely on one for a full shift outdoors.

Why does exercise make the same air so much worse for you?

At rest, you breathe roughly 6-8 liters of air a minute, mostly through your nose, which filters out some particles. During a hard run or ride, that climbs past 60 liters a minute, mostly through your mouth, which filters almost nothing. You're pulling in something like ten times the air, largely unfiltered, straight to your lungs. That's why "running or hard exercise" drops a full band earlier than everything else in the table — an AQI of 100 during a tempo run doesn't behave like a "Moderate" day for your lungs; it behaves more like "Sensitive groups" or worse. Coughing, chest tightness, or unusual fatigue mid-workout is your body telling you the dose is already too high. Stop — don't push through it.

Is staying inside automatically safer?

Only if your indoor air is actually cleaner than the air outside, and that's not automatic. An open window, a draft under a door, or a house that isn't well sealed will let outdoor PM2.5 fill your rooms within an hour or two. On bad days, keep windows and doors shut, run your AC on recirculate instead of fresh-air intake, and run an actual air purifier sized to the room — not just any filter, and not a unit sitting in a space three times too big for it. See how to size one for your home if you don't already have one running. Without filtration, a "sealed" house on a 200 AQI day can still drift into the 100s indoors by evening.

Does it matter what time of day you go out?

Yes, and it's easy to get fooled by a clear morning. Smoke levels can build through the day as regional smoke gets pulled down by daytime heating and shifting winds, so a spot that reads "Good" at 8 a.m. can read "Unhealthy" by 4 p.m. — and the reverse happens too. Don't lock in an outdoor plan off a morning glance; check again before you actually walk out the door, especially for anything longer than a quick errand.

So what should you actually do right now?

Skip the sky-gazing. Look up the live number for your city, run it against the table above — one column earlier if you or the person you're deciding for is in a sensitive group — and plan the next few hours accordingly. If the reading is already past 150 and the forecast says it's holding or getting worse, don't just wait it out: the same page shows you which nearby towns have cleaner air right now and how far the drive is. Sometimes the fastest fix on a bad smoke day isn't a mask or a purifier — it's forty-five minutes down the highway.

Sources & further reading. AirNow: AQI Basics, EPA: Particle Pollution, CDC: Air Quality & Health, American Lung Association: Clean Air.

This is general information, not medical advice. If you have a heart or lung condition, or you're caring for someone who does, talk to a doctor about your specific smoke-day limits.