A perfect storm of dry, windless weather and wood smoke has combined to create some of the worst winter air pollution in Sonoma County and the surrounding area in years.
The Bay Area Air Quality Management District said it would declare a record 11th straight winter spare-the-air alert Wednesday, making it illegal to burn wood, manufactured fire logs or other solid fuels for the next 24 hours.
Stagnant conditions have trapped fine particulate pollution close to the ground, creating a health hazard for everyone, especially children, the elderly and people with respiratory problems.
"It's like being in a smoky room where you can't open the windows," said Aaron Richardson, a spokesman for the district, which covers a nine-county region. "Nothing is leaving."
Richardson said the 11th consecutive no-burn day is nearly triple the previous record of four, reached in three previous seasons including last year.
But relief is in sight. Winds are expected to pick up late Wednesday, bringing fresh air from the ocean that will help reduce pollution levels over the next few days.
There's a slight chance of rain north of the Golden Gate this afternoon but the rest of the week is expected to stay dry, said National Weather Service meteorologist Roger Gass.
"The San Francisco area is set to have one of the driest calendar years on record," Gass said. "The next seven days look like that record may end up being set."
Stagnant air conditions could resume early next week, as the winds change direction and blow offshore again, he said.
Air quality officials said it is too soon to tell if the weather will trigger a burn ban on the days before Christmas.
"We've had to do it in the past," Richardson said. "We hope that won't be the case this year."
Wood smoke is the single largest source of wintertime pollution. It is comparable to cigarette smoke because it contains carcinogenic substances that are harmful to breathe.
Jenny Bard, a spokeswoman for the American Lung Association in the North Bay, said high concentrations can exacerbate asthma and are associated with heart attacks, strokes and premature death.
Tiny particles bypass airway defenses to enter directly into the lungs and bloodstream, causing cell damage and cardio-pulmonary illness, she said.
"There has been a lot of smoke in the air," Bard said. "We know it contains very harmful particles that have huge health impacts."
The buildup of smoke from 1.4million fireplaces and wood stoves in the Bay Area sparked the ongoing burn ban. A fire Tuesday at a recycling facility in Redwood City contributed to elevated levels of pollution.
During an alert, lighting a fireplace, wood or pellet stove, outdoor fire pits or other wood-burning devices is against the law.
Enforcement relies mostly on complaints from neighbors but about 70 air quality inspectors also fan out across the Bay Area, patrolling trouble spots day and night, Richardson said.
Last season, Sonoma County led the Bay Area in citations with 45 out of a total of 178 tickets. The season runs from November to February. The current year's statistics were not available.
First-time violators are required to take a wood smoke awareness course, online or by mail, or pay a $100 fine. Subsequent violations will result in a mandatory $500 ticket.