People who are staying in hotels, motels and resorts need more than their credit cards and clothing: A hyperbaric medicine expert at LDS Hospital says it's a good idea to take along a carbon-monoxide detector, as well.

Most lodging doesn't provide the devices, despite hundreds of injuries and dozens of deaths in the past 15 years related to carbon monoxide.

While hotels and motels are required by federal law to have a smoke detector in each guest room, there's no such mandate that carbon-monoxide detectors be furnished, said Dr. Lindell K. Weaver, medical director of LDS Hospital's Hyperbaric Medicine Center and co-author of a study that will be published in the July issue of the American Journal of Preventive Medicine.

Almost every hotel and motel has sources of carbon monoxide, including boilers, water heaters, furnaces and gas-fired dryers. The researchers found that sometimes carbon monoxide is also dragged into guest rooms from machinery being used outside.

Carbon monoxide is not something a person can detect unaided. It is clear, odorless and colorless. It's also potentially lethal. The commonly reported symptoms of carbon-monoxide poisoning include nausea, headache, generally not feeling well, fatigue and sometimes abdominal pain, tingling and muscle aches.

Those symptoms are usually felt when the level of carbon monoxide is low. When it's high enough, the patient is too impaired to feel symptoms and seek help, Weaver said.

To quantify incidents, the researchers combed local news reports, other publications and legal databases, and looked at other data on patients poisoned in lodging. They didn't count someone as a victim unless that individual was taken to the hospital to be treated, or died. They also did not count what could have been deliberate carbon-monoxide poisonings or poisonings that resulted from fires or related smoke.

In all, they documented 68 incidents with 772 victims from 1989-2004. In those cases, 45 incidents were related to room heating and 15 to tools and small boilers. Five came from outdoor sources.

The researchers found cases where boilers and furnaces had failed over time, he said, producing excess carbon monoxide that the ventilation system failed to clear. And the scientists said that their study underrepresents the total number of victims because not all incidents are reported to or by the media and not all cases of harm are recognized right away. It can take days and sometimes weeks for aftereffects of carbon-monoxide poisoning to be known.

When Jack Kevorkian was assisting suicides, he sometimes used carbon monoxide because "at pure concentration, it's lethal in seconds," Weaver said.

Without treatment, even those who survive experience problems, Weaver said. About half have new depression and anxiety. And without hyperbaric oxygen treatment, he said, half develop difficulty with cognitive thinking, which shows up within about six weeks.