Monday is a "Spare the Air" day in the North Bay, which means the use of wood-burning fireplaces, pellet stoves, wood stoves, fireplace inserts and outdoor fire pits is illegal.

The Bay Area Air Quality Management District notifies residents when particulate matter levels are anticipated to be unhealthy. On these days, the district issues alerts that prohibit wood burning.

Monday's air quality is expected to reach into the "unhealthy for sensitive groups" designation, which means that active children and adults and people with respiratory disease, such as asthma, should limit outdoor exertion.

The air on Tuesday may also be unhealthy for sensitive groups, according to the district. The determinations for the following days recommendations are made in mid-afternoon.

During winter, wood smoke is the largest source of soot pollution, according to the district.

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