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Breathing wildfire smoke can make you wheeze and cough. And it can trigger health emergencies — especially in people who have preexisting heart or lung conditions. So it’s critical to avoid smoky air.

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“Staying inside is what we often try to tell people, but staying inside isn’t always enough,” says Addison Houston of Seattle and King County, Washington’s public health department.

He says smoke can enter your home, so it’s important to filter the indoor air.

One option is to buy a HEPA — or high-efficiency particulate air — filter. But Houston says you can also build your own inexpensive, DIY solution.

All it takes is a 20-by-20-inch box fan and a furnace filter. Look for one rated MERV 13 and attach it to the back of the box fan.

“It actually pulls air through that filtration membrane as it’s operating and will effectively clear out the wildfire smoke, and functions really similarly to the level of efficacy that you see in a HEPA filtration unit,” Houston says.

Houston’s agency cautions that box fan filters should not be left unattended, and they should be periodically turned off so they do not overheat.

But the approach can help people protect themselves from wildfire smoke in a pinch, without breaking the bank.

Anesthesia Circuit Reporting credit: ChavoBart Digital Media