Air quality officials are extending Friday's Spare the Air alert into Saturday.
The Bay Area Air Quality Management District said air Saturday is expected to be unhealthy for sensitive groups. Those groups include people with respiratory illnesses such as asthma, bronchitis and lung disease and the elderly and active children and adults.
The pollution might exacerbate or aggravate respiratory illnesses, said BAAQMD spokesman Walter Wallace.
Indoor and outdoor wood burning is illegal when an alert is in effect except for people whose "sole source of heat" is wood, BAAQMD officials said.
"This is our air and we want to protect it," Wallace said.
The ban is in effect Saturday for Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, southern Sonoma and southwestern Solano counties, according to the BAAQMD.
The district says that particulates or soot pollution from wood smoke is the main source of pollution during wintertime.
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BAAQMD officials are asking residents to take steps to reduce pollution during alert days by walking, cycling or taking public transit.
"It's your air as well and together we want to protect it,"
Wallace said.
