The National Weather Service says a high pressure ridge over the Northwest is likely to cause air stagnation problems in Washington into next week.
Forecasters say a temperature inversion of warmer air aloft is trapping colder air close to the ground where wood smoke and vehicle exhausts build up. Without winds, the pollution could cause trouble for people with breathing problems.
The Weather Service has issued an air stagnation advisory for most of Eastern Washington.
Clean air agencies have burn bans in effect for several counties, including King, Pierce, Snohomish, Thurston, Clark and Yakima.