Another Winter Spare the Air alert has been issued for Saturday, the fourth regional wood-burning ban this week by the Bay Area Air Quality Management District.
A high-pressure weather system combined with cold temperatures have stayed in the Bay Area all week, trapping pollution that has accumulated to unhealthy levels, according to the air district.
On Winter Spare the Air days, it is illegal for Bay Area residents to burn wood, manufactured fire logs or any other solid fuels indoors or outdoors.
Homes without permanently installed heating are exempt from the ban, which forces violators to take a wood smoke awareness class or face a fine of $100, with rising fines for subsequent violations, district officials said.
The alert is the fourth issued by the district this week. Wood burning was also banned Friday and was earlier in the week on Monday and Tuesday.
Wood smoke contains fine particles and carcinogens and is the largest source of air pollution in the Bay Area during the winter, according to the air district.