Your Home Only Blocks 40–60% of Smoke—Yes, Even with the Windows Closed

Last week in Calgary was a smoky mess. Kids' soccer games were cancelled. Walks turned into headaches. And for a lot of us, staying inside felt like the only option.

But here’s the kicker: even with the windows shut, your home likely only blocked about 40 to 60% of that wildfire smoke.

That stat comes straight from Canadian experts who study indoor air quality. And it means most of us were still breathing in a good chunk of that haze—without realizing it.

So how does the smoke get in?

Even with everything closed up tight, smoke can still slip through:

• Open windows and doors (even for a few minutes

• Cracks in window seals, door frames, and siding

• Your HVAC system—especially if it pulls in outdoor air or runs with a basic filter

Older homes and homes without air conditioning tend to be leakier, too. And let’s face it—when it’s hot and smoky, you either cook inside or crack a window and let the smoke in.

How to prep now (while the air’s still clear):

Now that this week's looking better, it's a great time to get ahead of the next wave:

• Upgrade your furnace filter to a MERV 13 (or at least MERV 11)

• Run your HVAC fan continuously when it’s smoky out

• Seal any visible gaps around windows and doors

• Invest in a portable air purifier (or DIY one with a fan + furnace filter)

• Keep N95 masks handy for those with asthma or heart conditions

The takeaway:

We saw what poor air quality does last week—it cancelled plans, sent kids indoors, and reminded us how unpredictable wildfire smoke can be.

This week, the skies are clearer. Use the break to prep your home so next time, you're not scrambling to tape the windows or find a fan.