You’re in the Seattle area, smelling acrid smoke — like you’re at a bonfire. But why do air-quality apps show moderate-good or moderate air quality?

Among the possible reasons for these discrepancies, according to Dana Felton of the National Weather Service, is that the ribbon of smoke snaking from the Bolt Creek fire in Skykomish through Everett and into Seattle is very slim.

Because of that, sensors outside that band may be recording better air quality when it’s a different story just yards away.

“The swath of really bad air is narrow,” Felton said Wednesday. The reliability of individual apps, he said, is also dependent on the data they use and how often that data is updated.

Why you can’t necessarily trust your smartphone’s weather app

On Wednesday, AirNow — home of the U.S. Air Quality Index — indicated the air was unhealthy in Seattle and a large part of King and Snohomish counties. Readings from Puget Sound Clean Air Agency (PSCAA), however, showed only that the air was only “unhealthy for sensitive groups” in that same region.


Regardless of what the air-quality apps and websites say, trust your own experience and judgment first.

“When the air looks and smells smoky, it may not be the best time for activities outdoors. Use your best judgment,” said PSCAA said on its tips page.

The agency also suggest people check the sensor closest to their specific location, rather than the region.

Graeme Carvlin, air-quality scientist with PSCAA, said sometimes the smell of smoke can indicate moderate or worse air quality, but not always.

“It can be hard to tell,” he said. But protect yourself by masking up or going inside if you have symptoms such as a cough or stinging eyes, he said.

How to prepare for wildfire smoke in your home, car and while outdoors

Use an N95 or N100 mask when there’s smoke, the agency said. Other face coverings, like surgical or cloth masks, aren’t recommended due to limited protection from air pollution and wildfire smoke.

Carvlin said cleaner air is expected Thursday, when onshore winds are forecast to pick up. PSCAA recommends that while the smoke is here, folks limit their time outdoors and try to stay inside with windows and doors closed.

If you have a high-efficiency HEPA filter in your air cleaner or an HVAC system, turn it on. If you have an air conditioner, close the fresh-air intake to keep smoky air out of your home.