By BILL REED

McCLATCHY NEWSPAPERS

COLORADO SPRINGS, Colo.--Johnna Chapman was in the kitchen when she heard her 2-year-old daughter collapse. By the time she ran to the family room, the girl was convulsing on the floor.

Chapman screamed for her husband and called 911. She ran upstairs to put on clothes for the ambulance ride and passed out in her bedroom.

When firefighters arrived, they almost beat down the door before a groggy Randy Chapman turned the knob. The Chapman family was moments away from dying of carbon monoxide poisoning. Johnna, 7-year-old Brock and 2-year-old Megan were unconscious.

"It's everywhere," Johnna Chapman said of the deadly gas. "It's odorless. It's tasteless. It's colorless. It's truly the silent killer."

It was 1992, and the family had just moved to Colorado Springs, Colo. As the temperature dropped on that November night, dangerous levels of carbon monoxide collected in their rented house. They'd been running errands and were home about a half-hour when Megan collapsed at about 10:30 p.m.

She was the canary in the coal mine for the family--if they hadn't called 911 when she collapsed, they probably would have passed out before they got help.

Carbon monoxide poisoning kills nearly 500 Americans each year and forces about 15,000 to hospital emergency rooms, according to the Centers for Disease Control and Prevention.

Carbon monoxide-poisoning cases spike in winter, when gas furnaces are running and windows are locked tight. The most common symptoms are nausea, headache and dizziness--easily mistaken for the flu.

The more severe symptoms, such as loss of consciousness, shortness of breath and loss of muscle control, are rarely reported because by then it's usually too late.

An ambulance rushed the Chapmans to Memorial Hospital, where Johnna and Megan spent hours in the hyperbaric oxygen chamber. Carbon monoxide starves the body of oxygen and victims asphyxiate. Hyperbaric treatment is used to reverse the effects of carbon monoxide poisoning.

Johnna Chapman wasn't fully conscious for at least four hours, and a doctor told her he'd seen people die with lower levels of exposure.

"He told me, 'It was your pure determination as a mommy not to die that night,'" she said.

The four members of the Chapman family escaped without long-term damage.

"We have no long-lasting effects, although my children claim I do," Johnna Chapman said. "My goofiness has nothing to do with carbon monoxide."