SPOKANE, Wash. — Some areas of North Idaho are still experiencing poor air quality on Thursday.

The Kootenai Tribe area is sitting the "unhealthy for sensitive groups" range on Thursday, according to the Environmental Protection Agency. Cities like Pinehurst and St. Maries are in the "moderate" or "unhealthy for sensitive groups" ranges. 

Coeur d'Alene was in the "unhealthy" range on Wednesday but air quality there has since improved to "moderate." Spokane's air quality is also sitting in the "moderate" range on Thursday morning. 

One KREM viewer also reported on Wednesday that Rathdrum was buried in thick smoke.

With poor or declining air quality around the region, many residents may be wondering: why is this happening? The simple answer: stagnant air conditions.

Shawn Sweetapple, an air quality manager with the Idaho Department of Environmental Quality (DEQ), said a cold front from Canada recently moved into North Idaho. Now that the winds have died down, those cold temperatures are setting up inversions – especially in the mountain valleys.

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Temperature inversions occur when cold air close to the ground is trapped by a layer of warmer air, which leads to stagnant air and pollution that is trapped close to the ground. This often cause smog formation.

The National Weather Service has issued an Air Stagnation Advisory from Friday through Tuesday at 9 a.m. 

It is now open burning season, which means people can burn on their property without a permit from the Idaho Department of Lands, Sweetwater said. During a temperature inversion, the smoke can get trapped.

Sweetwater said there a few prescribed burns near Kellogg, Wallace and the St. Joe River drainage, but the DEQ has recommended restrictions on some larger prescribed burns due to conditions.

Those looking for information on open burning and woodstove conditions in their area can call 1-800-633-6247. Other questions can also be directed to airshed coordinators by calling 208-769-1422.

Daily air quality reports are also available on the DEQ website

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