, Page 00007 The New York Times Archives

AS you batten down the hatches to shut out winter's chill, keep in mind that some seasonal hazards come from within and can rise to dangerous levels when all the windows and doors are shut tight. The most common is carbon monoxide, an insidious vapor that can kill with little or no warning.

Improvements in venting systems and public warnings to consumers have resulted in a steady decline in carbon monoxide deaths in recent years. Still, more than 3,800 people will die from carbon monoxide exposure this year, and at least 10,000 others will be poisoned seriously enough to require medical attention or to miss a day or more of normal activities. Those who survive serious carbon monoxide poisoning can suffer brain damage causing memory problems, other intellectual impairments and personality changes like irritability, moodiness and aggressiveness.

Experts say at least one-third of carbon monoxide poisonings are never diagnosed, yet may result in subtle but significant impairments in brain and heart function. Even when symptoms are noticed, they are usually vague, nonspecific and easily confused with common ailments like the flu or depression, resulting in a missed or delayed diagnosis. Sources of Trouble

Carbon monoxide is a colorless, odorless and tasteless gas produced whenever organic, or carbon-containing, substances burn. Among common sources are tobacco smoke, motor vehicle exhaust, house fires, wood-burning stoves and fireplaces, factory machines with gas-powered engines, charcoal-burning barbecues, kerosene heaters and water heaters and furnaces that run on gas or oil.

When fuel-burning devices are improperly used, are poorly vented or malfunction, they can fill the air in an enclosed space with deadly carbon monoxide. A person breathing this air can be overcome before any symptoms are noticed.

Continue reading the main story

While about 40 percent of carbon monoxide deaths result from the deliberate use of car exhaust to commit suicide, most people who succumb to this product of combustion are unintended victims, like couples parked on lover's lane who leave the engine running and windows closed or families asleep when a furnace's exhaust system becomes clogged. A car parked with its engine idling in a single-car closed garage can produce lethal concentrations of carbon monoxide in 10 minutes or less.

Carbon monoxide also contributes indirectly to many deaths attributed to heart disease. Here the usual source is tobacco smoke. While most people who succumb are smokers, often the victims are nonsmokers whose spouses or co-workers subject their already compromised cardiovascular systems to carbon monoxide. Sidestream smoke contains twice the amount of carbon monoxide found in what smokers themselves inhale.

Other usually unsuspected sources of carbon monoxide are paint removers that contain methylene chloride, which is converted to carbon monoxide in the body. How It Harms

Once in the blood, carbon monoxide pushes oxygen out of its way and takes the place of this life-sustaining gas on the red blood cell pigment, hemoglobin, which normally carries oxygen to tissues throughout the body. Carbon monoxide has about 240 times the affinity that oxygen has for hemoglobin, which means that relatively minute levels of carbon monoxide in the air can build to rather high levels of carboxyhemoglobin (as the carbon monoxide-hemoglobin complex is called) in the blood.

The presence of carbon monoxide in effect pins oxygen to the ground, making it much more difficult for hemoglobin to release its oxygen to the tissues that need it. As the tissues become increasingly short of oxygen, the breathing rate automatically increases in a futile effort to take in more oxygen. But as long as carbon monoxide is present in significant amounts in the inhaled air, it will continue to displace oxygen on hemoglobin, creating a vicious cycle of ever-faster breathing and ever-rising blood levels of carbon monoxide.

Carbon monoxide also displaces oxygen on the muscle pigment, myoglobin, which can impair the function of skeletal muscles and the heart muscle. This can result in abnormal cardiac rhythms and severe chest pains caused by an insufficient supply of oxygen to the heart muscle. Prolonged exposure to low levels of carbon monoxide prompts the body to produce more red blood cells, which thickens the blood and forces the heart to work harder.

Fetuses are highly susceptible to carbon monoxide damage because fetal hemoglobin binds more tightly to this poison than adult hemoglobin does. Thus, the fetus may die even when a woman's exposure to carbon monoxide is not fatal to her.

Along with the heart, the brain is most vulnerable to carbon monoxide damage because it requires a steady supply of oxygen to function properly. Among typical symptoms of carbon monoxide poisoning are those related to impaired brain function, like headache, fatigue, weakness, dizziness, reduced ability to concentrate and irritability. Other frequent symptoms are nausea and shortness of breath. Less common signs are diarrhea, abdominal pain, vision problems and chest pain.

When carboxyhemoglobin levels exceed 50 percent, respiratory failure, convulsions or seizures, coma and death can follow.

Cigarette smokers typically walk around with carboxyhemoglobin levels from 3 to 8 percent, with occasional peaks of 10 to 15 percent. Nonsmokers who live in urban environments, where carbon monoxide is a common air pollutant, typically have levels of up to 2 percent carboxyhemoglobin. Prevention

Proper ventilation is the key to preventing carbon monoxide poisoning. Home furnaces and water heaters that run on fossil fuels must have unclogged vents and should be inspected each year. Motor vehicle exhaust systems must be kept in good repair to prevent leakage of exhaust fumes into the passenger compartment. Despite the high cost of fuel, it is unwise to make your house so tight that air circulates poorly. Consider sleeping with a window open; even a few inches can make a big difference.

Always follow rules about adequate ventilation when using equipment and chemicals. Know the proper way to fuel and use indoor heaters, wood-burning stoves and fireplaces. Have chimneys cleaned every year and make sure the flue works properly. Never barbecue in the house or in a closed shed or garage. And never leave the car running unless the garage door is opened to the outdoors.

Finally, don't smoke and don't let others fill the air you breathe with tobacco smoke.

Continue reading the main story