WAC 296-820-805 through 296-820-860 applies to all workplaces, including those with agricultural activity according to RCW 49.17.020, with the exception of the following:

(1) Enclosed buildings or structures in which the employer ensures that windows, doors, bays, and other exterior openings are kept closed, except when it is necessary to briefly open doors to enter and exit.

(2) Enclosed vehicles in which the air is filtered by a properly maintained cabin air filter and the employer ensures that windows, doors, and other openings are kept closed except when it is necessary to briefly open doors to enter or exit. Buses, light rail, and other enclosed vehicles used for transit systems where doors are frequently opened to board and deboard passengers are not included under this exemption.

(3) Work within the scope of chapter 296-305 WAC, Safety standards for firefighters.

(4) Workers performing prescribed burns.