Carbon Monoxide (CO)
Carbon Monoxide (CO) is a colourless, odourless poisonous gas
produced by incomplete, or inefficient, combustion of fuel
including 'cold' or badly tuned engines.
Badly ventilated domestic fuel appliances (gas, oil or solid fuel)
can cause high levels indoors, as can smoking.
As traffic is a major source of carbon monoxide, ambient
concentrations will generally be highest close to busy roads.
Monitoring data suggests that annual average CO levels have been
decreasing over the last few years. This is probably due to
improved vehicle engine efficiency and the introduction of
catalytic converters. The effect of technological improvements has
been cancelled out to some degree by an increase in traffic
levels.
Carbon Dioxide (CO2)
As opposed to carbon monoxide, carbon dioxide (CO2) is produced
by 'complete' fossil fuel combustion.
While ambient levels do not have any direct health effects, it
is an important 'greenhouse gas' which is believed to contribute to
global warming.
Its major anthropogenic (man-made) sources are road transport,
power stations and other industrial combustion processes and
domestic heating.
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