Mary and Bill Hultberg had a carbon monoxide detector in their house when the odorless, colorless gas nearly killed them - but it wasn't plugged into an outlet.

The detector had been going off during a remodeling project in a basement bathroom, so they unplugged it while painting. Mary Hultberg said it wasn't plugged in the morning she and her son became disoriented from the gas.

Now, the Hultbergs are big proponents of carbon monoxide detectors.

As soon as they returned to Bismarck from the Hennepin County Medical Center in Minneapolis, where they received hyperbaric oxygen therapy, the Hultbergs bought two digital carbon monoxide detectors. The detectors give digital readings of how much carbon monoxide is in the air so they know if the levels are rising.

Their friends also ran out and bought new detectors. Mary Hultberg said an e-mail with their saga has circulated, urging people to buy detectors.

"Irecommend everyone have one," she said.

"Of course it was a wake-up call for everybody," said Barbara Schmitt, a friend of the Hultbergs.

Mark Hanson, a spokesman for MDU Resources, agrees. People are urged to have at least one carbon monoxide detector on each level of their home or business, preferably placed in bedrooms, he said.

Bill Hultberg said the nature of carbon monoxide makes the gas so dangerous. You can't smell it like natural gas or smoke, he said.

"That's why it's so dangerous,"Hanson agreed.

Carbon monoxide can come from heating systems, gas-powered appliances and vehicle exhaust. Qualified technicians can check homes to make sure appliances are in good working order and are not leaking carbon monoxide, Hanson said.

"Any fuel-burning appliances should be checked"annually, he said.

A running vehicle inside or pulled part way out of an attached garage can lead to high carbon monoxide levels inside a house, Hanson said.

The Hultbergs also caution people to look for the early symptoms of carbon monoxide poisoning, which Hanson said can be mistaken for flu symptoms.

Mary Hultberg said she yawned constantly for several weeks before she and her son were hospitalized for carbon monoxide poisoning. Her neck had been swollen, and she had been having headaches. Now those symptoms are gone, along with a stiff neck Bill Hultberg had had for weeks prior to Jan. 24.

"Now everything's kind of loosening up,"he said.

Symptoms of carbon monoxide poisoning include headache, dizziness, flushed skin, disorientation, troubled thinking, abnormal reflexes, shortness of breath, fainting and convulsions. Exposure to the gas also can cause coma and death.

Bill advises people to be aware of the danger of carbon monoxide poisoning.

"It was something I never thought of until it happened,"he said.

(Reach reporter Jenny Michael at 250-8225 or jenny.michael@bismarcktribune.com.)