Sunday is another Spare the Air day, Bay Area air quality regulators declared, the 22nd no-burn day of the current cold spell.

The lack of wind and precipitation that normally clears out dirty, particulate-laden air is to blame for the unprecedented string of poor air quality, the Bay Area Air Quality Management District said.

On a Spare the Air day, it is illegal to burn solid fuels including wood or wood pellets, unless a wood-burning stove is the only source of heat in your home. Violators can be fined $100 or $500 for a second offense.