Macdonald Mechanical | Kelowna HVAC company

Is the Air Inside Your Home Safe During Wildfire Smoke Season?

Wildfire smoke over the Okanagan — protecting your home's indoor air quality

If you've spent a few summers in the Okanagan, you know how quickly the sky can change. One morning it's clear blue, and by afternoon a haze has settled over the valley and the smell of smoke is in the air. Most people's instinct is to close the windows and stay inside.

That's the right instinct — but staying indoors doesn't automatically mean you're breathing clean air. Wildfire smoke particles are extremely fine, and without the right setup, they'll find their way into your home and pass right through your HVAC system's filter unchallenged.

Here's what you need to know to actually protect the air inside your home during smoke season.

Why Standard Filters Don't Protect Against Wildfire Smoke

The filter in your furnace or air handler has a MERV rating — Minimum Efficiency Reporting Value. Most homes are running a MERV 8 filter, which is designed to catch dust, pollen, pet dander, and other large particles. It does that job reasonably well.

Wildfire smoke is a different problem. The particles in smoke — called PM2.5 — are 2.5 microns or smaller. To put that in perspective, a human hair is about 70 microns wide. A standard MERV 8 filter barely touches particles that small. The smoke moves right through it and continues circulating through your home every time your system runs.

What MERV Rating Do You Need During Smoke Season?

If you have a 4-inch media filter rack (the type that holds a thicker filter rather than the standard 1-inch slot), upgrading to a higher MERV rating is the most effective thing you can do:

MERV 8 — Standard filter. Handles dust and pollen. Minimal protection against smoke particles.
MERV 11 — Improved filtration. Captures some smoke particles. A meaningful upgrade over MERV 8.
MERV 13 — Recommended for smoke season. Captures fine particles at 50%+ efficiency. The best option for a standard filter-based system.

If you're still using a 1-inch filter slot, you're limited in how high you can go — thicker 4-inch media filters allow for both better filtration and better airflow. If you're not sure what you have, give us a call and we can take a look.

One Thermostat Setting That Makes a Real Difference

Here's a tip that costs nothing and makes an immediate difference during a smoke event.

On your thermostat, there are two fan settings:

AUTO — The blower fan only runs when your system is actively heating or cooling. When the system isn't running, air sits stagnant and unfiltered.
ON — The blower fan runs continuously, circulating air through your filter at all times — even when the system isn't heating or cooling.

During a smoke event, switching from AUTO to ON means your filter is working around the clock. If you have a good quality MERV 11 or MERV 13 filter installed, this single setting change can noticeably improve the air your family is breathing indoors.

Keep in mind that running the fan continuously does use more electricity than AUTO mode, but during a heavy smoke event, it's a worthwhile tradeoff.

When to Consider a Whole-Home Air Purifier

For most households, a MERV 13 filter combined with switching the fan to ON is a solid smoke-season strategy. But for some families, it may not be enough.

A whole-home air purifier integrates directly into your existing HVAC system, treating all the air that circulates through your home before it reaches your family. Unlike portable units that only cover one room, a whole-home system works throughout every room, every time your system runs.

It's worth considering if:

Anyone in your home has asthma, allergies, or a respiratory condition
You've noticed headaches, congestion, or worsening symptoms during smoke events
You have young children or elderly family members at home
Your smoke seasons have been getting progressively worse and longer

A Quick Smoke Season Checklist

Check your filter — if it hasn't been changed recently, replace it before smoke season
Upgrade to MERV 13 if your system supports it
Switch your thermostat fan from AUTO to ON when it's smoky outside
Keep windows and doors closed during high smoke days

Questions About Your Home's Air Quality?

Every home and HVAC system is different. If you're not sure what filter you have, whether your system supports an upgrade, or what options make sense for your situation, we're happy to take a look and give you an honest recommendation — no pressure.