Bay Area residents are being asked to avoid burning wood over the Thanksgiving holiday to keep air at a healthier level, officials with the Bay Area Air Quality Management District said.

Wood burning is allowed during the holiday weekend but discouraged because extensive burning could cause the air quality to become unhealthy, especially in inland valleys.

Air district officials are predicting moderately healthy air on Thanksgiving Day.

“We encourage residents to refrain from burning wood this holiday weekend to help keep air pollution low,” said Sharon Landers, interim executive officer of the air district. “Wood smoke creates unhealthy air inside and outside the home.”

Wood smoke contains small particles and carcinogenic substances that make the air unhealthy, causing concern for children, seniors and people with respiratory conditions.

Wood smoke is the Bay Area’s major source of pollution in the winter. One fireplace can pollute a whole neighborhood, air district officials said. Wood smoke has been tied to serious respiratory illnesses and a higher risk for heart attacks.

More than 90 percent of premature deaths from pollution are related to breathing fine particulates, according to the air district.