Once in the air it is readily absorbed through the lungs. It can also be formed in the liver from methylene chloride, a common component of paint remover and other solvents that are easily absorbed as vapor through the skin and lungs. This is one reason these products warn people to use them only with adequate ventilation. Once in the blood, carbon monoxide latches tightly onto hemoglobin, the molecule in red blood cells that carries oxygen to every cell in the body. The affinity that carbon monoxide has for hemoglobin exceeds oxygen's attraction by about 240 times.
Most people normally have at most only a few percent of their hemoglobin as carboxyhemoglobin.
Smokers have much more than nonsmokers, and those who live or work in environments polluted by tobacco smoke are likely to have even higher levels of carboxyhemoglobin than smokers themselves. As levels rise to 10 percent or more, symptoms of poisoning start to appear. As carboxyhemoglobin levels rise, victims may experience shortness of breath, rapid heart beat, difficulty concentrating, confusion, visual problems, chest or abdominal pain and muscle cramps. The most severe cases of carbon monoxide poisoning result in loss of consciousness and death. This page, and other ASH web pages, may be freely copied and reproduced in print or on other web pages.