The air this week was filled with soot and tiny specks, triggering a wood-burning ban Friday for all eight Valley counties from Stockton to Bakersfield. It was the first Valleywide burning ban this fall.

The bad-air episode is expected to continue through the weekend, said the San Joaquin Valley Air Pollution Control District. It is the result of stagnant weather that allows fine particles to build up over many days.

"There's not a lot of wind," said Errol Villegas, program manager for district air quality analysis. "It has also been cold, and people have been burning wood."

A burning ban makes it illegal to ignite wood, pellets and manufactured fire logs in fireplaces and other devices, such as wood-burning stoves, according to the district.

Residents are encouraged to check with the air district before lighting a fire at home.

The buildup of soot, chemicals and other fine particles began last weekend, creating federal air violations in Fresno. By Thursday, violations were recorded in Fresno, Clovis, Hanford, Bakersfield, Modesto, Turlock and Sequoia National Park.

Fine particle pollution is linked to early mortality, asthma and heart ailments.

Children, senior citizens and people with lung problems should limit their time outside when such pollution spikes.

And Valley residents should refrain from burning wood during district-ordered bans, officials said.

"Particulate emissions from wood-burning not only can re-enter your home and affect your indoor air quality, but they also directly affect your neighbor," said district executive director Seyed Sadredin.