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Carbon monoxide

CO , coal gas, carbon(ic) oxide, flue or exhaust gas

SPRI Emission Reporting Threshold
100,000 Kg/yr Pollutant Emissions to Air
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Carbon monoxide is a colourless, odourless gas. It is formed both naturally and by man's activities when fuels containing carbon are burnt in low-oxygen conditions.
What is it used for?
In the past, the main use of carbon monoxide was as a constituent of "town gas". This was used for domestic heating until it was replaced by the much less toxic natural gas (which contains mainly methane). Today, carbon monoxide is used in metal refining and in the production of certain chemicals.
Where does it come from?
The main source of carbon monoxide is from petrol vehicles which are not fitted with a catalytic convertor. Carbon monoxide levels in urban areas closely reflect traffic density (in combination with weather conditions). Other man-made sources are power stations and waste incinerators. At a domestic level, faulty gas appliances and cigarette smoking are significant sources of carbon monoxide. Natural processes produce relatively small amounts.
How might it affect the environment?
Carbon monoxide reacts with other pollutants in the air to form potentially harmful ground level ozone. This occurs close to the site of emission. It does not have any significant environmental effects at a global level.
How might exposure to it affect human health?
Inhalation of carbon monoxide at high concentrations can be fatal, because it prevents the transport of oxygen (in blood) around the body. Releases from poorly maintained appliances in poorly ventilated spaces could result in concentrations high enough to cause death. Long-term exposure to lower concentrations (such as through smoking) could harm unborn babies or cause neurological damage.
What steps are being taken to limit the potential impacts?
The main legislation controlling levels of carbon monoxide in the UK (including Scotland) is the National Air Quality Strategy. Carbon monoxide is one of the eight key air pollutants targeted for direction. It is also regulated by the European Directives on ambient air quality assessment and management (96/62/EC); and on combating of air pollution from industrial plants (84/360/EEC).