From the text:'Among Forest Service activities, prescribed burning, slash disposal and forest fires present the greatest potential for polluting the air. But at this time we do not know what kind of pollution it is, how dangerous it is, how much of it there is, if it is a pollutant at all, and if so, what the best ways are of minimizing its effect and still get our fire job done. Annually we burn in excess of 130,000 acres of slash and besides that a small acreage for fuelbreak purposes and other reasons. Currently a total systems or air shed approach is being recommended for combatting air pollution. This includes identifying broad air zones, determining all causes of pollution within the zone and then developing a program to reduce or control these causes to acceptable limits of pollution output. Such an approach will, of course, include our burning activities.