How Wildfire Smoke Seasons Affect Your HVAC Filtration Needs

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Why wildfire smoke is harder on your filter

Everyday household dust and pollen are relatively large particles that even a basic filter will catch a fair share of. Wildfire smoke is different. It's dominated by very fine particulate (the kind measured as PM2.5), which is small enough to slip through cheap fibreglass or low-rated filters and recirculate through your home. That's why a filter that seems 'fine' the rest of the year can feel useless when the sky turns orange.

In Metro Vancouver, late summer smoke drift from BC's Interior and beyond has become a regular part of the season. When it settles in, your furnace or air handler fan is often the main tool you have to keep indoor air cleaner, so the filter in it is doing real work rather than just protecting the equipment.

What filter should you run during smoke season

The practical answer for most homes is a good pleated filter in the MERV 11 to 13 range. Higher MERV numbers capture more of the fine smoke particulate. MERV 13 is often the sweet spot for smoke because it removes a large share of PM2.5 while still being something many residential systems can handle.

A few things to keep in mind before you jump to the highest-rated filter you can find:

• Higher MERV filters restrict airflow more. If your blower isn't sized for it, you can starve the system, reduce comfort, and in some cases cause the furnace to overheat and shut down.
• Match the physical size and thickness to your filter slot. A thicker media filter usually flows better at a high MERV than a thin one-inch filter.
• Change it far more often during smoke events. A filter that lasts three months in clean air can clog in weeks when it's pulling smoke.
• Don't cram in a filter the system wasn't designed for and assume more is always better. If you're unsure, it's worth a quick check.

Protecting your HVAC system while running it hard

During a smoke event you'll often want to run the fan more, sometimes continuously, to keep pulling air through the filter. That's reasonable, but it means the filter loads up fast. Check it every week or two while smoke lingers, and keep a spare on hand so you're not stuck with a clogged one when the air is at its worst.

Keep windows and outside-air intakes closed during heavy smoke, run your AC or heat pump in recirculate rather than pulling in outdoor air, and if you have a portable HEPA air cleaner, use it in the rooms where you spend the most time. The HVAC filter and a portable unit work well together.

If your home is tightly sealed and you have an HRV or ERV, understand how it behaves during smoke. These systems bring in fresh outdoor air, which is the opposite of what you want on a bad smoke day, so many can be switched to a low or recirculate setting temporarily.

When it's worth calling a professional

If you want to move to a MERV 13 filter and aren't sure your system can handle it, or your furnace is short-cycling and shutting off when you install a higher-rated filter, that's a good time to have it checked. The fix might be a thicker filter cabinet, a media filter upgrade, or confirming your blower can handle the added resistance.

CANRO Heating & Cooling is a licensed HVAC contractor based in Burnaby, serving Metro Vancouver since 1999. We can look at your filter setup, confirm what your system will safely support, and recommend upgraded filtration or a dedicated air-cleaning solution if that makes sense for your home. Call (604) 359-1081 or email info@canroheat.ca and we'll set up a visit with a free written quote.

Frequently asked questions

Reviewed by the CANRO Heating & Cooling service team — July 07, 2026. Technical Safety BC gas licence LGA0043870 · boiler licence LBP0046450 · Red Seal certified · WorkSafeBC and liability insured · 4.9★ from 85+ Google reviews · serving Metro Vancouver since 1999 · (604) 359-1081.