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Carbon monoxide, chemical formula CO, is a colourless, odourless, flammable and highly toxic gas. It is a major product of the incomplete combustion of carbon and carbon-containing compounds.

carbon monoxide poisoning symptoms

Carbon Monoxide binds very strongly to the iron atoms in haemoglobin, the principal oxygen-carrying compound in blood. The affinity between CO and haemoglobin is 200 times stronger than the affinity between haemoglobin and oxygen. As CO binds to the haemoglobin, it cannot be released nearly as readily as oxygen would be. Thus, the body's haemoglobin becomes saturated with CO and is rendered incapable of carrying oxygen to the body. A sufficient exposure to carbon monoxide can reduce the amount of oxygen taken up by the brain to the point that the victim becomes unconscious, and can suffer brain damage or even death from anoxia. The brain regulates breathing based upon carbon dioxide levels in the blood, rather than oxygen, so a victim can succumb to anoxia without ever noticing anything up to the point of collapse. Haemoglobin acquires a bright red colour when bound to carbon monoxide, so a casualty of CO poisoning can actually look abnormally pink-cheeked and healthy. Thus, symptoms of carbon monoxide poisining can be hard to diagnose at first.

A major problem of accidental carbon monoxide poisoning that still exists is the use of heaters, particularly gas water heaters and gas fires which are improperly vented. A number of deaths occur every year from this cause. CO poisoning can occur in SCUBA diving due to faulty or badly sited diving air compressors.

First aid for carbon monoxide poisoning is to immediately remove the victim from the exposure without endangering oneself, call for help, apply CPR and if possible apply oxygen first aid. Hyperbaric oxygen therapy is a treatment for carbon monoxide poisoning.

physiological role

Carbon monoxide is produced naturally by the body. The breakdown-product of haemoglobin, haeme, is a substrate for the enzyme haeme oxygenase which produces CO and biliverdin. The biliverdin can then be reduced to bilirubin which is excreted by the liver. The CO produced in the brain might act as a neurotransmitter.

sources of carbon monoxide poisoning

Carbon monoxide has many common sources. The exhaust of the internal combustion engine, when burning a carbon-based fuel (i.e. almost any fuel except pure hydrogen) contains carbon monoxide, especially when the temperature is too low to effect complete oxidation of the hydrocarbons in the fuel to water and CO2, because the time (i.e., the residence time) available in the combustion chamber is too short, or because there is insufficient oxygen present. Usually, it is more difficult to design and operate a combustor for very low CO than for very low unburned hydrocarbons. Carbon monoxide is also present in small but significant concentrations in cigarette smoke. In the home, CO gas forms when fuels like natural gas, oil or wood do not burn completely in appliances such as furnaces and stoves, water heaters, ranges and ovens. Thus, common sources of carbon monoxide include leaky heat exchangers in furnaces; improperly or blocked vents for gas appliances, fireplaces and stoves; idling vehicles in attached or underground garages; or large collections of idling vehicles. Carbon monoxide gases can percolate through concrete hours after vehicles have left a garage.