Damage to the body can begin very quickly from large amounts of carbon monoxide. How quickly this happens depends on the length of time a person is breathing the gas and the amount of the gas he or she breathes in. Another consideration is how much alcohol the person might have to drink.

SHIRLEY GRIFFITH: Carbon monoxide poisoning has warning signs. But people have to be awake to recognize them. Small amounts of the gas will cause a person’s head to hurt. He or she may begin to feel tired. The person may feel sick. The room may appear to be turning around. The person may have trouble thinking clearly.

People develop severe head pain as the amount of gas continues to enter their blood. They will begin to feel very tired and sleepy. They may have terrible stomach pains.

BOB DOUGHTY: Carbon monoxide is measured in parts per million in a normal atmosphere. Breathing in two hundred parts per million of carbon monoxide will cause the first signs of poisoning. It will result in head pain, stomach problems and a feeling of tiredness after two to three hours.

A level of eight hundred parts per million will cause a person to lose consciousness. Victims will not know what is taking place around them. This will happen within two hours of breathing in this amount of carbon monoxide. Twelve thousand parts per million of the gas will cause death in one to three minutes.

SHIRLEY GRIFFITH: Medical experts say carbon monoxide affects people differently. For example, a small child will experience health problems or die much quicker than an adult will. The general health of the person or his or her age can also be important.