Wildfires may keep you inside more often this summer. Is it safe to run the AC?

As wildfires rage across the country and cast a haze over Canadian skies, many people are staying indoors seeking refuge from the smoky air. Is it OK to run their air conditioner?

As wildfires rage across the country, casting a dark haze over Canadian skies, many people are staying indoors seeking refuge from the smoky air.

But as temperatures heat up in some parts of the country, Canadians may be left wondering if turning on their air conditioners will bring unwelcome smoke and pollutants into their homes.

“It’s a little bit complicated. For most Canadians, if they have air conditioning in their home, there is no outdoor air that comes in with that air conditioning,” said Jeffrey Siegel, an engineering professor at the University of Toronto, who also studies indoor air quality.

“And so turning on the air conditioning is a good thing to do to keep the temperature down, and it’s an especially good thing to do if you have a good filter in place.”

But it depends on the filter and the air conditioner, he said.

While some air conditioners can effectively reduce pollutants from wildfire smoke and improve indoor air quality, there are others that might draw smoke into your home.

“Wildfire smoke is made up of a whole soup of pollutants,” explained Dr. Samantha Green, a family physician at Unity Health Toronto. “And the one that we worry most about is referred to as PM 2.5, and that’s because it not only irritates the nose, the throat and the eyes, but it can get deep into the lungs and then into the bloodstream.”

Short-term exposure to smoke can cause eye irritation, runny nose, sore throat, wheezing, shortness of breath and a tight sensation in the chest, she said.