Faulty heating systems, power blackouts, and the use of cheaper but dangerous heating methods during difficult economic times make fall and winter the prime time for deaths caused by carbon monoxide, often called the "invisible killer, but year-round vigilance is important."

Carbon monoxide is a colorless, odorless and highly toxic gas produced mainly by the incomplete combustion of fuel. It is easy to overlook the symptoms of carbon monoxide poisoning, and prolonged exposure can be fatal.

"People don't realize that they might be subjected to it," Carmine Gianatiempo, M.D., says, "because they can't perceive it."

Director of critical care at Englewood Hospital and Medical Center, Gianatiempo says that carbon monoxide poisoning is "relatively common." Accidental exposure accounts for an estimated 15,000 emergency room visits and 500 unintentional deaths in the U.S. each year.

Science

Carbon monoxide is dangerous both because it's difficult to detect and because of its insidious effect on the human body. The toxic gas attaches itself to blood cells and suffocates a victim from within.

Hemoglobin, the part of red blood cells that delivers oxygen throughout the body, has a much greater affinity -- 240 times greater, Gianatiempo says -- for carbon monoxide than for oxygen. So in the case of a carbon monoxide leak, hemoglobin readily bonds with the toxic gas, effectively starving the body of life-giving oxygen.

Symptoms

In its early stages, the symptoms of carbon monoxide poisoning are deceptively mundane: a headache, fatigue, nausea, maybe vomiting.

"So basically," Gianatiempo says, "people think they have the flu. Many times it's overlooked."

As exposure progresses, a victim can suffer confusion or impaired motor functions in moderate cases and seizures, coma or death in extreme cases. Exposure also can cause delayed neurological problems, Gianatiempo says, which manifest as much as two months after treatment and can persist for as long as a year.

Treatment

For most cases of carbon monoxide poisoning, treatment is straightforward. For minor to moderate exposure, breathing through an oxygen mask for 90 minutes can clear out half the carbon monoxide from one's system.

Extreme cases sometimes require the victim to enter a high-pressure, super-oxygenated hyperbaric chamber. That last resort isn't always an option, though Ð Englewood Hospital is the only hospital in Bergen that has hyberbaric chambers, Gianatiempo says.

Precautions

Fortunately, preventing carbon monoxide poisoning is fairly simple. Most important, make sure your carbon monoxide detectors are functioning properly and replace them at least every five years. Also, get all fuel-burning appliances, including furnaces, gas ovens and fireplaces, inspected yearly.

Beyond that, never use any fuel-burning device, from chainsaws to generators, unless you're outdoors or in a well-ventilated area. Never idle the car in a garage, even if the garage door is open. And never use a gas oven to heat the kitchen or the house, even for a short time. 

Fast Facts: Carbon Monoxide (CO)

• It is colorless, odorless and highly toxic.
• It attaches to blood vessels and deprives the body of oxygen.
• Mild cases resemble the flu while extreme cases can cause coma or death.
• The blood normally contains 2 to 3 percent CO. Smokers' blood contains 10 to 15 percent. Levels of 20 to 25 percent are dangerously toxic.
• Maintain CO detectors and replace every five years.
• Never heat a home using a gas oven.
• Use fuel-burning devices only with proper ventilation.

What to do?

If you suspect that you or someone else has been exposed to CO, follow these steps:

• Get fresh air immediately. Open doors and windows.
• Call your gas company if you smell gas or suspect a leak.
• Get to the hospital or call an ambulance for emergency care and say that you suspect CO poisoning. Doctors need to perform a test specifically for checking CO levels in the blood.