Spare the air alert declared through Friday as smoke lingers over Bay Area

As heavy smoke from the Camp Fire in Butte County continues to choke Bay Area skies, a Winter Spare the Air Alert has been extended through Friday.

Burning wood, including manufactured logs or any other solid fuel, indoors or outdoors is banned through Friday, the Bay Area Air Quality Management District announced today.

While weather conditions will vary throughout the week, air quality is expected to remain unhealthy because smoke is trapped at the surface and surrounding the region, air district officials said.

"Any additional smoke from Bay Area chimneys could push the region into an even higher unhealthy air quality level, which puts us all in jeopardy," Jack Broadbent, executive officer of the air district, said in a statement.

Bay Area residents should limit outdoor activity as much as possible on days when the alert is in effect, and should continue to listen to health information from local authorities.

When air quality is unhealthy, it's best to stay indoors with doors and windows closed. Masks should not be used instead of remaining indoors, but if worn, they should be a new, clean N95 mask or greater that's securely strapped for a tight seal.

Masks aren't suitable for men with beards or young children, according to the air district.

Like cigarette smoke, wood smoke contains fine particles and carcinogenic substances that make the air harmful to breathe inside and outside. Wood smoke is the major source of air pollution in the Bay Area during the winter and is especially harmful to children, the elderly and those with respiratory conditions.