Wildfire smoke is in our homes. Here's how to clear out toxic particles

As the smoke from hundreds of out-of-control wildfires dances and lingers above hundreds of North American communities, experts warn about the risks to human health from toxic particles those clouds carry. 

And because no home is perfectly sealed, air quality indoors can still be affected.

"On average, whatever the air pollution level outside is — inside is probably about half that," explains Dan Westervelt, associate research professor at Columbia University's Climate School.

"And so when you're talking about the kind of levels that we've been seeing in the Mid-Atlantic U.S., half of that is still pretty dangerous."

So what are some ways this smoke can enter our homes?

Naturally, the largest openings in our homes to the outside tend to be the doors and windows. But even when they're closed, says Amy Li, an air quality expert at Waterloo University, smoke particles can still "infiltrate into your room through all the cracks and leakages in the building enclosure." 

Another source people may not consider is the ventilation system in some buildings. Intentionally designed to bring fresh air into an apartment or condo, Li says the particles could be carried in through these systems. 

"It's interesting because typically we need the fresh outdoor air to address indoor pollutants," Li said, recalling the need for fresh air in recent years to reduce transmission of COVID. "But in this case we do not want it if it's not filtered."

Closing those doors and windows is the first step during days where the Air Quality Health Index indicates a high health risk, experts say. 

Li also suggests if you know of any areas in your home that leak air from the outside or carry a draft, they can be blocked with cloths or towels. 

It's important to keep indoor air circulating, as these wildfire seasons typically coincide with hot summer temperatures. Heat's effect on the human body can take many forms and air conditioning systems can help — with the right filtration and air source. 

"You want to make sure that your ventilation system is on, and that you have some good quality air filters on your ventilation system," suggested Roshini Kassie, a specialist at the Water and Air Quality bureau at Health Canada. 

Kassie reiterates that systems should be recirculating air, not drawing it from the outside. For apartments, Li suggests examining the air handling unit, which is typically in its own cabinet.

"Check if it has a high efficiency filter," Li described. "If you notice that the existing filter is really dirty, then maybe consider replacing the filter."