By Dave Larsen and Katherine Ullmer
The Dayton Daily News

HARRISON TWP., Ohio — Carbon monoxide can be a silent killer that can be especially dangerous on winter nights.

A mother and three children ages 3 to 18 almost died early Wednesday morning, Feb. 10, when a malfunctioning furnace filled their home at 4425 Thompson Drive with odorless, colorless carbon monoxide.

The mother called 911 to report that she felt ill. Firefighters found the woman and the children unconscious inside, where the carbon monoxide level had reached the lethal level of 190 parts per million, said Harrison Twp. Fire Chief Mark Lynch.

The family was taken to Kettering Medical Center in critical condition. They were released from the hospital late Wednesday morning.

"Everybody's asleep and they don't realize they're getting into trouble," said Bill Wharton, spokesman for Public Health — Dayton & Montgomery County.

Carbon monoxide poisoning "is very common throughout the winter months," especially when people attempt to use auxiliary heat sources during a power outage, Wharton said. It kills about 500 annually nationwide, according to the Centers for Disease Control and Prevention.

Carbon monoxide detectors can be purchased for less than $20. "They're every bit as important as a smoke detector," Wharton said.

The Harrison Twp. Fire Department provides free carbon monoxide detectors to township residents, Lynch said.

CO problems are often caused by incomplete combustion in furnaces or water heaters. Wharton suggested that home owners check to "make sure that flame in there is burning blue and not bright yellow." If it's not burning blue, you might need to have the furnace or water heater professionally cleaned or adjusted, he said.

Copyright 2010 Dayton Newspapers, Inc.