Air Pollution Control Areas

Several Missoula Air Pollution Control Program Rules are location-specific. In addition, due to historic air pollution violations, Missoula has a PM10 nonattainment area and a carbon monoxide maintenance area. Choose from the links below to learn more about air pollution control areas in Missoula County.

Missoula Air Stagnation Zone

The Missoula Air Stagnation Zone (MASZ) extends about four miles outside Missoula City Limits. The MASZ affects woodstove, paving and outdoor burning rules. Visit the Missoula Air Stagnation Zone page to learn more about the rules that apply within its borders.


Impact Zones

There are two Impact Zones in Missoula County. Impact Zone M includes all of the City of Missoula, Frenchtown, Lolo, and East Missoula. Impact Zone SL surrounds Seeley Lake. The Impact Zones primarily affect outdoor burning rules and Air Pollution Warnings. Visit the Impact Zones page to learn more about these areas.


Nonattainment and Maintenance Areas

Missoula was designated nonattainment for PM10 in 1990. The resulting nonattainment area primarily impacts industry rules.

Missoula is currently in maintenance for carbon monoxide. The carbon monoxide maintenance area does not have rules more stringent than those already in place in the Air Stagnation Zone.

Visit the Missoula Nonattainment and Maintenance Areas page to learn more about Missoula's history with these pollutants, current projects and rules that are impacted by their boundaries.


Oxygenated Fuel Control Area

In order to reduce carbon monoxide pollution, fuel sold for on-road motor vehicle use in the oxygenated fuel control area must include some ethanol between Nov. 1 and the end of Feb. For more information about this program check out our Frequently Asked Question page.