Pacifica, CA- A family of three escaped possible death Tuesday morning when a carbon monoxide detector in their home alerted the residents, who had already started feeling ill, to the presence of the odorless, toxic gas, a fire official said.

An ambulance took a mother, father and child from their house in the 400 block of Carmel Avenue to the hospital around 7:30 a.m. as a precaution, said North County Fire Authority spokesman Matt Lucett. Their injuries were not life-threatening.

“Oh yes, it could have saved their lives,” Lucett said of the carbon monoxide detector.

Family members were feeling nauseated and lightheaded and called for help when the alarm installed in their home began to sound.

Once firefighters were at the scene, they tested the air and discovered about 400 parts per million of carbon monoxide gas. One or two hours of exposure at that level could cause the symptoms felt by the family, Lucett said.

Breathing the gas for 15 minutes at a concentration of 6,400 parts per million could cause death, Lucett said, citing figures from the National Fire Protection Association. Longer exposure to lower levels can also be dangerous.

Pacific Gas and Electric Co. workers went to the house to determine the source of the gas, which was apparently a furnace.

Lucett said the family had not done anything overtly dangerous to fight the low temperatures, like burn charcoal or run a generator indoors.