Wildfire Smoke Season in the Fraser Valley: How to Keep Your Indoor Air Safe

Smoke season is no longer a rare event in the Fraser Valley; it's a recurring part of late summer, sometimes arriving in the same week as a heat wave. The good news: with the right filter, the right fan setting, and a few preparations, your home can be a genuine refuge while the sky outside is orange.

We're Rep-Air Heating and Cooling, a locally owned heating, cooling, and air quality company in Mission, BC, licensed through Technical Safety BC and serving the Fraser Valley since 2017. We live here too, what follows is the same checklist we run in our own homes when the smoke rolls up the valley toward Mission and Chilliwack.

What's Actually in Smoke, and Why PM2.5 Matters

Wildfire smoke is a mix of gases and particles, but the component that does the harm is fine particulate matter, PM2.5: particles small enough to slip past your nose and throat, reach deep into the lungs, and enter the bloodstream. Those same tiny particles are why smoke gets indoors: they ride in through open windows, door gaps, and building leaks, and once inside they linger. Everything below is really one strategy: keep PM2.5 out, and filter out what gets in.

"Does My AC Pull Smoke In?", Clearing Up the Big Misconception

Every smoke season, homeowners tell us they shut off their air conditioning because they were afraid it was sucking smoke into the house. It isn't. A central AC or heat pump recirculates the air already inside your home: it doesn't draw outdoor air in. With windows closed and decent filtration in place, running your central system during a smoke event is one of the best things you can do: every pass through the filter takes more particulate out.

Your central system with a good filter is a whole-home air cleaner during smoke events. Turning it off out of caution is exactly backwards.

This is also where cooling and air quality stop being separate topics. The real Fraser Valley scenario, the one the 2021 heat dome taught us, is heat and smoke at the same time. A heat pump or AC lets you keep every window shut and stay cool, which is the whole game during a smoke event. If your home still can't do that, our heat pump vs. furnace guide for Fraser Valley homes explains why built-in cooling has become the deciding factor for so many households here.

Your Before-the-Season Checklist

The best smoke-event response is set up in June, not improvised in August:

• Upgrade the filter, with one caveat. A MERV 13 filter captures fine particulate effectively, but it also adds airflow resistance. Have a technician confirm your blower can handle it first: a filter that's too restrictive strains the blower and can even freeze an AC coil. Standard low-MERV fibreglass filters, for the record, do very little against smoke.
• Know your HRV's recirculation mode. Find the control now and learn to switch it : mid-event, with the house hazy, is the wrong time to read the manual.
• Place a portable HEPA unit in the bedrooms. Portable HEPA air cleaners are the best supplement to central filtration, and bedrooms, where you spend eight hours at a stretch, are where they earn their keep.
• Make sure you can cool with the windows shut. If your only cooling strategy is open windows, smoke season takes it away exactly when you need it.
• Stock spare filters. Smoke loads filters fast; you'll change them more often than the box suggests.

Filtration Options Against Smoke, Compared

During a Smoke Event: The Settings Walkthrough

• Close the windows and doors: and keep them closed, including overnight when it's tempting to air the house out.
• Set the system fan to ON, not AUTO. On AUTO the blower only runs during heating or cooling calls; ON keeps air moving through the filter continuously, scrubbing particulate all day.
• Switch the HRV or ERV to recirculation mode. These ventilators bring outdoor air in by design, exactly what you don't want mid-event. No recirc mode? Run it at its lowest setting, or turn it off briefly during the worst of it. Don't leave it off for days: tight newer builds especially will develop humidity and stale-air problems without ventilation.
• Run your cooling as normal: remember, it recirculates; it doesn't pull smoke in.
• Check the filter mid-event if the smoke lingers. Heavy particulate can load a filter in a fraction of its normal life.

A note on why the fan setting earns its own line item: most homes run the blower on AUTO, which means on a mild smoky day (no heating call, no cooling call) the system might barely run at all, and the filter you upgraded sits idle while particulate drifts through the house. Flipping to ON is free, takes ten seconds at the thermostat, and is probably the single highest-value move on this list. The trade-off is simply that a continuously running blower loads the filter faster, which is why the mid-event filter check is on the list too.

After the Smoke Clears

• Change the filter. Whatever it caught during the event, you don't want your system breathing through it for months.
• Return the HRV to its normal ventilation mode: fresh air exchange matters again the moment the outdoor air is clean.
• Keep checking filters through the season. Smoke events tend to come in waves; the filter that survived one event may not have much left for the next. Filter care folds neatly into regular service, our guide to how often your furnace should be serviced covers what a proper tune-up includes.

When to Get Help

Some of this you can do with a stepladder and a shopping list. The rest is where our licensed team comes in, explore our indoor air quality services for the full picture, or go straight to the specific fix:

• Blower can't take a MERV 13 in the existing slot? A filter cabinet installation adds deep media filtration without the airflow penalty.
• Just want it checked? We'll confirm your blower's filter compatibility during any service visit, reach out and ask.

Locally owned, BBB accredited, and holding 4.9 stars across 500+ Google reviews, we'd rather set your home up right in June than take an emergency call in August.