A program identified by the Clean Air Act to prevent air quality and visibility degradation and to remedy existing visibility problems. Areas of the country are grouped into 3 classes which are allowed certain degrees of pollution depending on their uses. National Parks and Wilderness Areas meeting certain criteria are "Class I" or "clean area" in that they have the smallest allowable increment of degradation. 

According to the American Meteorological Society, the net force per unit area exerted by the atmosphere as a consequence of gravitational attraction exerted upon the column of air lying directly above the point in question.  Atmospheric pressure is independent of the orientation of the surface on which it acts.

Atmospheric pressure corrected for elevation.

A calculated reduction in actual payload to provide a margin of safety.

Set of computerized FIREMODELS run during fire season at the operations coordination center on preselected locations to indicate possible fire spread from those points for that date.

Personnel who have reported to the incident without an assignment (i.e., they are not assigned to an increment, strike team, or organizational unit).

Thickness of a liquid, the degree to which it resists flow.

Term used to describe any facility that is used for the coordination of agency or jurisdictional resources in support of one or more incidents.

The mathematical average of the maximum and minimum relative humidities measured at a fire weather station from one basic observation time to the next.

Time of day required to record meteorological data at a fire danger station.