Smoke has filled valleys on the eastern slopes of the Washington Cascades and air pollution monitors in several towns indicate the air is hazardous to breath, KUOW-FM, Seattle, reported.
The Kittitas County Public Health Department has been sent 10,000 masks, with another 12,000 going to adjacent Chelan and Douglas counties.
The masks offer "limited" help from the fouled air, health officials said, cautioning residents to stay indoors as much as possible.
"Smoke from wildfires has ranged into the 'unhealthy' and 'hazardous' categories in several areas, according to local health officials," the Washington State Department of Health said in a statement.
The department had stockpiled the masks for use during the H1N1 swine flu outbreak.
Other counties hit hard by smoke include Whitman, Okanogan and Yakima, the department said.
The agency cautioned that infants and young children, pregnant women, adults over 65, and people with existing heart and lung conditions are particularly vulnerable to wildfire smoke.