Residents are asked to limit driving. Burning wood is illegal during Spare the Air days.

The San Francisco Chronicle says it’s the eighth Spare the Air day since Dec. 7.

Bay Area Air Quality Management District spokesman Ralph Borrmann says skies appear to be clear, but cold air near the ground is trapping pollutants and creating a health hazard.

Residents are urged to take bikes, public transit or carpools instead of driving solo, to cook indoors rather than barbecue and to avoid using gas-powered gardening equipment.