Saturday has been declared a Spare the Air day, banning wood burning in the Bay Area on Christmas Eve.

In a season characterized by images of families keeping warm by the fire, the Bay Area Air Quality Management District declared Saturday to be a Spare the Air day, meaning that Bay Area residents are prohibited from burning wood indoors or outdoors.

“Winter air pollution is mainly caused by particulates or soot pollution from wood smoke,” according to the alert. “Smoke from wood-burning fires is linked to illnesses such as asthma, bronchitis and lung disease, and is especially harmful for children and the elderly.”

The air district issues alerts when the concentration of particulate matter in the air could violate state and national health standards, according to the Spare the Air website. This is the ninth alert of the Winter Spare the Air season, which runs from Nov. 1 to Feb. 29. Last season, there were four.