Carbon Monoxide (outdoor)

Carbon monoxide (CO) is a colourless, odourless, tasteless and non-irritant gas that is slightly lighter than air.

It is well known as a poisonous gas produced by the incomplete combustion of fuel.

CO enters the body through the lungs, where it is absorbed by the bloodstream and it acts by combining with the haemoglobin in red blood cells and so reducing oxygen carriage by the blood. At levels below those which are lethal, this reduction in oxygen-carrying capacity can precipitate angina in those susceptible and reduce mental performance, resulting in confusion and reduced co-ordination.

With concentrations of 20 to 30% of carbon monoxide-haemoglobin symptoms can include shortness of breath on moderate exertion and slought headache. Concentrations from 30 50% cause severe headache, mental confusion and dizziness, impairment of vision and hearing and collapse and fainting on exertion. With concentrations of 50 60 % unconciuosness results, and death may follow if exposure is long.

Repeated exposure to low concentration of the gas,up to 100ppm in air, is generally believed to cause no signs of poisoning or permanent damage.