NO2 is nitrogen dioxide more correctly abbreviated as no2. For convenience and for

simplicity we shall use the correct chemical description with no2 in brackets for ease

of reference. NO2 is one of a number of oxides of nitrogen, including the best known

one i.e. nitrous oxide (N2O) popularly known as laughing gas. NO2 is a chemical that

formed during the production of nitric oxide. As such it is an important intermediate in the

production of nitric acid. And millions of tons of nitric acid are manufactured every year for

industrial use. NO2 (no2) is a highly toxic gas and appears as red fumes, with a particularly

sharp, bitter smell. If sufficient NO2 is inhaled, it will destroy enough of the person’s

respiratory tract to cause severe lung problems and even death. NO2 is heavier than air

and therefore sinks down when released. The gas is a so-called free radical because it has a

free electron. The chemical composition of NO2 makes it combustible with carbon

containing chemicals. On occasions, when the gas burns it does so explosively. The biggest

producer of the gas is car engines. But other prominent sources of the gas are thermal power

stations and pulp mills. Burning of butane gas for domestic and industrial use also produces a

substantial amount of NO2 . The gas is a large scale pollutant, particularly in rural areas.

It may also have a part to play in sudden infant death syndrome or SIDS. Interestingly, it

produces the reddish tinge of the mushroom cloud during explosions of atomic and hydrogen

bombs. On a more positive side NO2 is converted into nitrogen products by the

lightening in electrical storms. As such it is an important component of the nitrogen cycle

which is essential for life on earth. As a result, rain that follows an electric storm has a

relatively high nitrogen content making it an excellent fertiliser.

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