On a cold and long drive during Christmas vacation when the Smith family stopped to take a break, the parents were horrified to find their two young sons dead in the back seat. Carbon monoxide had leaked in from the engine exhaust.

The above episode is but one of many involving carbon monoxide poisoning, which is quite common in today's society. An estimated 10,000 victims seek medical care yearly, excluding the 1,000 accidental and 2,300 suicidal carbon monoxide-related deaths. Some experts feel that these figures represent only the "tip of the iceberg."When a generous supply of fresh air is available and the fuel is burning properly, little danger of carbon monoxide poisoning exists.

Everyday sources of carbon monoxide include automobile exhaust; faulty wood stoves, kerosene heaters, poorly ventilated natural gas heaters and furnaces and sources involving any organic material burning.

Carbon monoxide also is responsible for many deaths in fires. In fact, most fire victims never see or touch the flames but are poisoned by toxic gases or carbon monoxide.

Exposure to carbon monoxide is often unsuspected by its victims. The gas is colorless, odorless and non-irritating. The signs and symptoms of poisoning can be misinterpreted by the victim and even by medical personnel.

Signs and symptoms include:

-Headache

-Angina (chest pain)

-Nausea and vomiting

-Dizziness and visual dimming

-Collapse and coma

Carbon monoxide produces its toxic effect by combining with hemoglobin to form carboxyhemoglobin, which causes a decrease in the oxygen transport capacity of the blood and impairs the use of oxygen by tissues. The gas's affinity for binding to hemoglobin (red blood cells) is 200 times greater than that of oxygen.

Contrary to popular belief, the cherry-red color of the skin and mucous membranes are not commonly seen - only at autopsy.

FIRST AID:

Immediately remove the victim from the toxic environment. Those exposed should be immediately moved into fresh air and given 100 percent oxygen by either an ambulance attendant or hospital emergency room staff.

Sometimes people are exposed to carbon monoxide in amounts that do not threaten their lives but do make them feel dizzy or sick. Other actions to consider include:

-If the person is conscious, seek medical attention involving a blood test to determine the level of carbon monoxide.

-If the person is unconscious, place him on his side and maintain body heat.

-If the person has stopped breathing, give either mouth-to-mouth resuscitation or CPR if you have been trained.

Even when only mild symptoms (headache or nausea) appear, it may be a good idea to check with a physician if you suspect carbon monoxide poisoning.

(SB) Alton Thygerson is a professor of health sciences at Brigham Young University.