Those planning to gather around a crackling fireplace on Christmas Eve will have to make other plans. That's because air quality officials have issued another burn ban for today.

The Spare the Air alert issued by the Bay Area Air Quality Management District bans indoor and outdoor burning of wood or any other solid fuel in the nine-county Bay Area. Small, rural sections of northern Sonoma and Solano counties are exempt, as are homes that rely exclusively on wood stoves or fireplaces for heat.

"We want everyone to enjoy the holiday," said district spokesman Ralph Borrmann, "but we also want people to be healthy while doing so."

The ban is the 17th of the season and the result of unusually dry, stagnant winter conditions that trap tiny, carcinogenic particles produced by wood burning at ground level. That creates health risks, especially for the very young, old and those with respiratory problems.

With stagnant conditions expected to continue through Christmas, it's possible that Bay Area air quality could reach the unusually bad level of "very unhealthy," Borrmann said.

Those who violate the burn ban are required to take a wood smoke awareness course, online or by mail, or pay a $100 fine. Second violations lead to a $500 ticket, with additional tickets even higher.