The Bay Area's coldest months of the year are the times when wood burning is banned on winter Spare the Air days.
The Bay Area Air Quality Management District typically calls about 10 of the health alerts during the burn season that lasts from Nov. 1 to Feb. 28.
Forecasters issue the 24-hour alerts when they expect cold stagnant air will trap smoke and other fine particles near the ground, bringing pollution concentrations close to or exceeding public health limits set by the federal government.
First-time burn violators must take a smoke education class at home or online or pay a $100 fine. Second-time violators are fined $500.
Burn violators are unlikely to know they have been spotted until they get a mailed citation days later.
While they must actually see the smoke to make a case, the inspectors who issue citations do not knock on the door or initiate contact with the offender. Inspectors take notes and often snap a photo of the smoke before turning their report over to other air district employees who decide whether to issue a citation.
People who live in rural areas without access to natural gas for heating can get exemptions from the ban.
The nine-county air district has about 70 inspectors. Most spend the bulk of their time inspecting refineries, factories, power plants and other businesses.
On Spare the Air days, the district diverts some inspectors to smoke patrol in residential areas.
On a typical Spare the Air day, district inspectors check out some 18,000 homes. That still is a small fraction of the 1.4 million homes in the region with fireplaces or wood stoves.
In addition to the no-burn rule, inspectors also enforce a rule barring excessively dense smoke or burning of trash or plastics any time of the year.
To sign up for email or phone notices of Spare the Air alerts, go to sparetheair.org or call the air district at 800-430-1515. To complain about smoke, call 877-466-2876 (4NOBURN).
Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.