The Bay Area Air Quality Management District issued the season's ninth Winter Spare the Air alert for today.
The order bans burning wood, manufactured fire logs or any other solid fuel, indoors and outdoors for 24 hours, except for homes that have no other source of heat.
Regulators said the light wind and rain mid-week failed to flush out fine particle pollution that reached unhealthy levels and threatens to do so again today.
Violators of the ban have the option to take a wood smoke awareness class, online or by mail, to learn about the hazards of wood smoke pollution in lieu of paying a $100 penalty. Second violations result in a $500 ticket; subsequent ticket amounts are higher.