CA – By Craig Koscho, The Calaveras Enterprise

Fending off the autumn chill made three employees ill at the Chevron convenience store in Valley Springs and forced the closure of Highways 12 and 26.

The workers were overcome by carbon monoxide fumes Monday afternoon when a heating unit was turned on for the first time this season.

Emergency crews got a call shortly after 2 p.m. that the workers were ill and there was an odor in the area of the store on west Highway 26, Undersheriff Mike Walker said.

Sheriff’s deputies and local firefighters cordoned off the store, evacuated the surrounding area and called the county’s Hazardous Materials Team.

Dressed in protective gear, two team members entered the store and took air samples while two others waited outside.

The samples were immediately tested in the team’s mobile unit and revealed levels of carbon monoxide ranging from 4 to 10 parts per million, sheriff’s Capt. Clay Hawkins said.

That’s in keeping with the victims’ symptoms such as headache and nausea, Hawkins said, adding that the suspected culprit was a heater employees had used for the first time this autumn.

Some health experts set a zero level carbon monoxide as safe, with the health hazard rising dramatically above 30 ppm.

Team members had completed their first test of the building and been decontaminated by 3:25 p.m.

Hawkins said at that time they would vent the building then re-enter it and take another sample.