Mild carbon monoxide poisoning causes headache, nausea, vomiting, drowsiness, and poor coordination. Most people who develop mild carbon monoxide poisoning recover quickly when moved into fresh air. Moderate or severe carbon monoxide poisoning causes confusion, unconsciousness, chest pain, shortness of breath, and coma. Thus, most victims are not able to move themselves and must be rescued. Severe poisoning is often fatal. Rarely, weeks after apparent recovery from severe carbon monoxide poisoning, symptoms such as memory loss, poor coordination, and uncontrollable loss of urine (which are referred to as delayed neuropsychiatric symptoms) develop.

Carbon monoxide is dangerous because a person may not recognize drowsiness as a symptom of poisoning. Consequently, someone with mild poisoning can go to sleep and continue to breathe the carbon monoxide until severe poisoning or death occurs. Some people with long-standing, mild carbon monoxide poisoning caused by furnaces or heaters may mistake their symptoms for other conditions, such as the flu or other viral infections.

Carbon monoxide poisoning is diagnosed by measuring the level of carbon monoxide in the blood.

HEALTH HAZARD INFORMATION  (From NIOSH)

Contributor's note: This stuff may be hard to read, but it is necessary to an understanding of how the medical community approaches this subject and how the U.S. government deals with complaints.

* Summary of toxicology

1. Effects on animals - (deleted for space considerations. See OSHA website. Get there via Google.)

2. Effects on Humans: Carbon monoxide is an asphyxiant in humans. Inhalation of carbon monoxide causes tissue hypoxia by preventing the blood from carrying sufficient oxygen. Carbon monoxide combines reversibly with hemoglobin to form carboxyhemoglobin. The reduction in oxygen-carrying capacity of the blood is proportional to the amount of carboxyhemoglobin formed [Gosselin 1984]. All factors that speed respiration and circulation accelerate the rate of carboxyhemoglobin formation; thus exercise, increased temperature, high altitude, and anemia increase the hazard associated with carbon monoxide exposure[Gosselin 1984]. Other conditions that increase risk are hyperthyroidism, obesity, bronchitis, asthma, preexisting heart disease, and alcoholism [NLM 1993]. In tests with human volunteers breathing 50 ppm carbon monoxide (a concentration that produces 27 percent carboxyhemoglobin after an exposure of 2 hours), there was a significant decrease in time to onset of exercise-induced angina[Gosselin 1984].

Carbon monoxide can be transported across the placental barrier, and exposure in utero constitutes a special risk to the fetus. Infants and young children are generally believed to be more susceptible to carbon monoxide than adults. The elderly are also believed to be more susceptible to carbon monoxide poisoning [Gosselin A carboxyhemoglobin level of 0.4 to 0.7 percent is normally present in the blood of adults. In cigarette smokers, the range is 4 to 20 percent, which places smokers at greater risk in exposure situations [Clayton and Clayton 1982; ACGIH 1991]. A capacity to adapt to carbon monoxide exposure has been reported in several human studies.

Healthy young men exposed to carbon monoxide at a concentration of 44 ppm for a prolonged period suffered no adverse health effects [ACGIH 1986]. Men exposed to 50 ppm for several days without relief complained of headaches, but exposure to 40 ppm for 60 days was without effect [ACGIH 1986]. Workers in the Holland Tunnel working 8-hour swing shifts of 2 hours in and 2 hours out at an average carbon monoxide exposure concentration of 70 ppm had average carboxyhemoglobin levels of 5 percent, and none had levels above 10 percent [ACGIH 1991].