Cozy wintertime fires made scarce in recent times by air pollution rules would become even more rare under a valleywide proposal aimed at easing respiratory ills.
Fireplace restrictions would more than double "no-burn" days in some valley counties, scientists predict, leaving as little as 28 days each winter when fires might be allowed.
In addition to home wood burning, proposed rules are likely to affect restaurants that charbroil, lawn-care providers, asphalt companies and some farmers.
Studies predict that air quality in the valley's northern counties -- Stanislaus, San Joaquin and Merced -- will nearly meet federal standards by 2014 and would surely do so by 2017 without new restrictions, thanks to regulations imposed in recent years.
But some southern counties such as Kings and Kern might not, so air officials will consider stricter rules on everyone for particulate matter, known as PM-2.5.
"Public health is our No. 1 priority," said Errol Villegas of the air district in a workshop last week on the air district's plan to address PM-2.5.
The name reflects the tiny size of air particles from dust and soot -- smaller than 2.5 microns, meaning you could put about 25 bits side-by-side to reach the width of a human hair. Although microscopic, they harm sensitive lungs, aggravating asthma, causing lung cancer and prematurely killing hundreds of valley residents each year.
"This really is a wintertime problem," said Jon Klassen, a district senior air quality specialist. That's why the air district a few years ago instituted no-burn days based on air quality forecasts, during which people can't light fireplaces without risking fines.
Vehicles, particularly diesel trucks, are a significant source of particulate matter, but the air district has less control over that pollution source.
Preventing fires throughout the San Joaquin Valley -- Stanislaus, San Joaquin, Merced, Madera, Fresno, Kings, Tulare and Kern counties -- keeps 16.7 tons of particulate matter from the air, studies show.
"No other single regulation achieves this level of effectiveness," reads a draft plan heading to a December vote by air district officials.
District staff members want to lower the threshold for triggering no-burn days, from readings of 30 micrograms per cubic meter to 20, by November 2014. If the valley doesn't meet federal standards by 2019, a contingency rule could lower the trigger to 15 micrograms per cubic meter.
Draft rules addressing particulate matter would put new restrictions on:
Charbroiling. Restrictions on chain-driven charbroilers, in which meat moves on a conveyor belt through a compartment heated above and below, have reduced pollutants. New rules would address charbroilers fired underneath.
Some new home furnaces fueled by natural gas.
Some boilers, steam generators and process heaters.
The district additionally will consider new rules on flares, lawn-care equipment and requiring lower temperatures when mixing asphalt. Another idea involves sending crop remnants to a biomass burner.
Officials say they will consider expenses associated with proposed rules before adopting them. A vote is expected Dec. 20.
Meeting the federal standard could prevent people throughout the valley from missing 100,262 workdays in 2019 because they wouldn't be sick, said David Lighthall, the air district's health science adviser. About 528 people would not die early from breathing problems, he said.
According to Lighthall's analysis, other health benefits from cleaner air for Stanislaus County alone include 23 fewer emergency room visits for respiratory distress; 16 fewer hospitalizations for heart attacks; 84 fewer acute bronchitis attacks; 6,292 fewer asthma episodes; and 39 fewer premature deaths.
On the Web: www.valleyair.org/Air_Quality_Plans/PM25Plans2012.htm.
Public comments on the draft plan can be submitted by Oct. 23 to email@example.com or to Anna Myers, 1990 E. Gettysburg Ave., Fresno 93726.