MISAWA AIR BASE, Japan — As indoor heaters crank up this winter, base officials are reminding residents to be mindful of the dangers of carbon monoxide, an odorless, colorless and tasteless gas that can cause sudden illness and death.

Base medical officials would not say how many carbon monoxide cases they treat each winter, but they said it’s a continuing issue.

“A lot of individuals come in, maybe a handful every winter” with symptoms of carbon monoxide overexposure, said Capt. Leslie Stapp, a 13th Fighter Squadron flight surgeon who works at the base hospital.

Stapp did say that several months ago, 15 persons in a base choir group reported to the emergency room after accidentally inhaling carbon monoxide fumes while singing at an off-base church. Two with more severe symptoms were treated at a Japanese military base. The church’s heating ventilation system appeared to be damaged, funneling carbon monoxide gas back into the building, Stapp said.

Created when fuel burns, carbon monoxide is the leading cause of poisoning death, accounting for more than 500 unintentional and 1,700 suicide deaths in the United States each year, according to the Iowa Statewide Poison Control Center.

Most who report to Misawa’s emergency room with carbon monoxide sickness live off base, where most homes are heated with kerosene or natural gas, Stapp said

Symptoms include headache, dizziness, weakness, nausea, vomiting, chest pain and confusion, according to the Centers for Disease Control and Prevention.

“It can literally put you to sleep without having too many symptoms,” Stapp said. “You can become unconscious before you realize what’s happening. A lot of people say they just feel like they’re getting drunker and drunker. That’s why it’s so dangerous.”

People who believe they’ve been exposed to carbon monoxide should seek fresh air and medical treatment immediately, Stapp said. Hyperbaric oxygen treatment is used in more severe cases. Newsday.com reported in a December 2004 online article that hyperbaric treatment takes place in a sealed chamber with portholes. Patients breathe in pressurized oxygen — the equivalent of being 66 feet under water — that dissolves carbon monoxide in the red blood cells.

Misawa’s base hospital has what’s referred to as a hyperbaric module — it’s like a chamber but smaller, Stapp said.

Patients also may be hooked to an oxygen machine to alleviate symptoms.

“Because people may be sensitive to their medical treatment, we just don’t discuss the numbers,” said Capt. Daniel Roberts, chief of the Human Performance Training Team, 35th Medical Group, in explaining why hospital officials would not discuss how many people they’ve treated this winter and last for carbon monoxide exposure.

But carbon monoxide sickness “is a factor here,” he said. “It has been a factor and will probably continue to be a factor.”

Maj. Monte Harner, 35th Civil Engineer Squadron operations flight commander, said several precautions can help keep homes safe.

Americans’ off-base homes in Misawa most commonly are heated by portable kerosene heaters or natural gas- or kerosene-fueled furnaces, he said.

With a pre-installed heating unit that vents to the outside, residents should ensure snow or other debris hasn’t blocked the vents. “If it is blocked, carbon monoxide will be forced back into the house,” Harner said.

The landlord should be involved in checking vents periodically, Harner said. “The standard off-base lease states the landlord is responsible for maintenance and upkeep of the heaters. They should schedule safety checks and regular cleanings of the heaters and propane gas ranges.”

Although some houses already come with a carbon monoxide alarm, usually installed next to the stove, Harner said keeping at least one tester near the sleeping area is smart. Misawa’s base exchange sells combination carbon monoxide and smoke detectors for about $35.

Heaters in newly built homes should shut off automatically if carbon monoxide is detected, but having a backup still is a good idea, Harner said.

Although no carbon monoxide is produced when heat is turned on in base housing — the system runs on steam — base residents need to be careful with portable heaters using kerosene or others combustible fossil fuels, Harner said.

“Make sure you purchase one that can be vented to the outside. It should have a vent tube that you can vent to a window,” he said.