"It’s a bit of an upstairs-downstairs situation," the agency says, and downstairs, the air is clean.

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That smoky haze tinting the sun red and the ash floating around aren’t as bad for you as they look, according to scientists.

Despite the nasty appearance of the Puget Sound region’s air on Tuesday, it’s mostly safe to breathe, said Michael Schmeltz, an air-quality scientist with the Puget Sound Clean Air Agency.

Though there are some isolated areas, like in North Bend and Crystal Mountain, where it’s recommended residents avoid physical exertion outdoors, most of the rest of Snohomish, Pierce, King and Kitsap counties has only moderate air quality.

“It has to do with the size of the particles,” Schmeltz said. Large particles of ash like the ones landing on cars around the Seattle area can irritate eyes, noses and throats, but don’t penetrate deeper into the lungs.

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Those larger particles are caught by the lungs’ cilia, which filter out anything larger than 2.5 microns. A human hair, by contrast, is about 50 or 60 microns, according to a spokesperson at Washington’s Department of Ecology. Particles smaller than that zip right by the cilia and can cause damage to the lungs.

Small particles in the air, which can penetrate the lungs’ defenses, are staying high in the atmosphere, around 5,000 feet above Seattle, Schmeltz said. At ground level is mostly cleaner air swept in from the north and west. Since the Puget Sound is closer to these fires than it was to the fires in British Columbia last month, wind isn’t pulling smoke in at ground level.

“It’s a bit of an upstairs-downstairs situation,” the agency said in a Facebook post; while bigger, heavier particles sink down from upstairs, the air downstairs is clean so far.

Nevertheless, sports are cancelled Tuesday at some schools, like Tacoma Public Schools and Kent School District. Schmeltz says there’s no reason to cancel activities based on air quality itself, but school districts could be concerned about ash irritating students.

Other parts of Washington are not so safe: Spokane’s air quality is the worst since the intense wildfires of 2015, according to The Spokesman-Review, and Spokane’s regional health district has recommended canceling all outdoor activities. Wenatchee, Ellensburg, Yakima and Colville have very unhealthy air quality in which anyone could start to experience health problems, according the Department of Ecology. Many other parts of Eastern Washington have air-quality levels that are unhealthy.

The Department of Ecology warns that this could change, possibly lowering air quality in some areas to “unhealthy for sensitive groups” later Tuesday, according to Larry Altose, a spokesperson for the department. Seattleites can stay updated via Puget Sound Clean Air Agency’s Facebook page or Twitter.