An inversion that has been trapping stagnant air in the Missoula valley for the last several days has triggered a Stage One Air Alert.

Air Quality Specialist Ben Schmidt with the Missoula City-County Health Department said the alert was declared early Tuesday morning.

"We've had this persistent high-pressure ridge over the area, however, with this pool of cold air hovering on the valley floor we're just getting nowhere," Schmidt said. "Basically, the air pollution has been climbing the last few days so we had to call a Stage One Air Alert today."

Schmidt said persons in sensitive groups, such as children the elderly and those with respiratory problems should limit their time outside during the alert, and the use of wood stoves is not allowed, with very few exceptions.

"If you have a wood stove or fireplace, you may not have any visible emissions in the Missoula Air Stagnation Zone," he said. "That's a pretty big area, not just the city limits. It includes most of Lolo, all of East Missoula, out to the Wye. The only people who can use their wood stoves are those that have pre-existing Stage One Air Alert permits that were issued prior to 1994."

Schmidt said the alert could last several days, or until a weather system strong enough to move the stagnant air out of the valley comes through, which may be by the weekend.