Fire is an inevitable and ecologically important process that maintains the health of forest ecosystems in the Western United States. A century of fire suppression has increased fuel loads to the point that inevitable wildfires often burn too fast and too hot to be contained, thus overwhelming suppression efforts. In response, national forests in the West are increasingly using large prescribed fires, as well as allowing the moderate spread of unplanned wildfires under favorable conditions, to make forests more resilient to drought, bark beetle outbreaks, and wildfires under extreme conditions. Land and resource management plans for many of these national forests are undergoing revisions that are likely to increase the use of fire in wildlands to achieve resource objectives. Such efforts create a growing challenge for land managers and air regulators who are charged with minimizing impacts to air quality in nearby communities.