It could be confusing to say the least to look out your window, see the thick smoke layer is still there, then glance at your phone to check the air quality only to discover it says it's "good."

A similar confusion could set in if you had glanced at the overall state Department of Ecology's current air quality page which amid the dozens of "very unhealthy" and "hazardous" readings of the past week around Western Washington have shown a few isolated spots "in the green" with seemingly crazy low numbers, especially in places like Ferndale and Issaquah.

No, Issaquah did not invent some magical city-wide smoke force field or 200-foot tall air purifier as I had guessed -- it was just as bad there as everywhere else. The simple answer is the measuring sensor there only measures ozone, not particulate matter from smoke like the majority of the other stations.

"It operates during the summer when elevated ozone may occur due to higher temperatures," says Graeme Carvlin with the Puget Sound Clean Air Agency.

Good news: We don't currently have an ozone pollution problem.

But we surmise these online weather apps are simply programmed to snag the air quality from the closest sensor, not accounting for what the sensor actually measures. So while Issaquah's ozone reading is in the good category, it's missing the important fact that the particulate pollution is very much NOT in the good category.

Carvlin says the Bellevue sensors all do measure particulate. So if you adjust your app there you could get a more accurate reading. Also be sure on regional maps like this one to just search "PM2.5" and not "All" to weed out those non particulate sensors.

Why do the air quality numbers vary by site?

So as people flock to find their current air quality, you might have noticed you could find some conflicting numbers out there. Turns out there are a couple different scales for measuring air quality that suggest a different hazard level for the same amount of pollution.

With heavy smoke the current issue, air quality managers are mostly concerned with particle pollution.

"The instruments that measure particle pollution report their data in units of micrograms per meter cubed (g/m3). These measurements are then converted to the Air Quality Index (AQI), the familiar green to maroon scale," Carvlin says. "The benefit of the AQI is that is combines multiple types of air pollution into one number. If ozone were high then the AQI number would reflect the high ozone. During this smoke episode, the AQI reflects the high particle pollution."

The AQI was what the Puget Sound Clean Air Agency uses.

But the Washington State Department of Ecology, our state air quality agency, has their own scale called the Washington Air Quality Advisory (WAQA).

"The WAQA has lower limits for each AQI color. For example, a particle pollution level of 25 g/m3 is yellow (moderate) on the AQI scale, but orange (unhealthy for sensitive groups) on the WAQA scale," Carvlin says. "Because the WAQA scale has lower limits it is more protective of health."

To recap: This map uses the WAQA Scale, while this map uses the Puget Sound Clean Air AQI scale. By the way, the popular AirNow Site uses AQI.

So this means when you're hunting around different sources for air quality readings nearby, you could be seeing variable results depending on which sensor your source is using, when it was last updated, and even which scale it is using for measurements.