Regional haze refers to visibility impairment in federal class 1 areas caused by pollutants emitted from specific geographic regions.
Sources: Hardy, Colin C., Ottmar, Roger D., Peterson, Janice L., Core, John E., and Seamon, Paula. 2001. Smoke Management Guide for Prescribed and Wildland Fire 2001 Edition. Produced by the National Wildfire coordinating Group Fire Use Working Team.