Carbon monoxide is a colourless, odourless, tasteless, non-irritating and highly toxic gas.
When inhaled, carbon monoxide reduces the ability of blood to carry oxygen.
Carbon monoxide is by far the most common single cause of poisoning both in industry and in homes. Thousands of persons succumb annually as a result of CO intoxication.
A sizeable proportion of the workforce in any country has a significant occupational CO exposure. CO is an ever-present hazard in the automobile industry, garages and service stations. Road transport drivers may be endangered if there is a leak of engine exhaust gas into the driving cab. Occupations with potential exposure to CO are numerous, e.g. garage mechanics, charcoal burners, coke oven workers, cupola workers, blast furnace workers, blacksmiths, miners, tunnel workers, Mond process workers, gas workers, boiler workers, pottery kiln workers, wood distillers, cooks, bakers, firemen, formaldehyde workers, and many others. Welding in vats, tanks or other enclosures may result in production of dangerous amounts of CO if ventilation is not efficient. The explosions of methane and coal dust in coal mines produce 'afterdamp' which contains considerable amounts of CO and carbon dioxide. If ventilation is decreased or CO emission increases owing to leaks or disturbances in process, unexpected CO poisonings may occur in industrial operations that usually do not create CO problems.
Automobiles produce the largest amount of carbon monoxide. Reduction of CO emissions from recent-model automobiles has been offset by a 34% increase since 1970 in the number of vehicles on the road and by an increase in the number of miles driven. Without pollution controls, the total carbon monoxide emitted would have increased significantly. Overall, CO emissions have changed little since 1970.