A record-setting fifth consecutive Spare the Air alert was called for Thursday in the Bay Area, triggering yet another 24-hour ban on burning wood fires in fireplaces and stoves.

Prolonged cold stagnant air is trapping smoke and other fine particle pollutants near the ground.

While forecasters expect the weather to warm up a little on Thursday, the change was not enough to avert a Spare the Air alert called for the fifth day in a row by the Bay Area Air Quality Management District.

The alerts are called when the district forecasts smoke and other fine particle concentrations that will violate a federal health standard designed to prevent breathing problems in people -- especially the sick, the elderly and young children.

"This stagnant weather pattern continues but we are pleased residents are abiding by the burn ban to help protect Bay Area air quality," Jack Broadbent, the air district's executive officer said in a written statement. "The fine particulate pollution in wood smoke is as hazardous as cigarette smoke and is the number one air-pollution-related health concern in the region."

Santa Clara County on Thursday is expected to have the dirtiest air exceeding federal health standards. But high pollution concentrations close to the standard also are expected in the East Bay, North Bay and the Peninsula, air quality officials said in a forecast.

The alert bans wood fires in fireplaces, stoves, open pits and other devices except in homes areas where there is no alternative ways to heat buildings.

The string of air quality alerts could end Friday with warmer temperatures, but that decision won't be made until early Thursday afternoon.

Thursday is the ninth Spare the Air alert of the district's winter air pollution season, which lasts from Nov. 1 through Feb. 28.

The district regulates air pollution in seven Bay Area counties and southern parts of Solano and Sonoma counties.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.