Nitrous oxide is a colorless, non-flammable gas. It has a
slightly sweet taste and odor. It is non-toxic and non-irritating
and when inhaled in small quantities can produce mild hysteria and
giggling or laughter. This is where the nickname "laughing gas"
comes form. When inhaled in pure form it will cause death by
asphyxiation because at atmospheric temperatures and pressure, the
oxygen in nitrous oxide is not available to the body.
A property of nitrous oxide is that at about 565 degrees F, it
breaks down into nitrogen and oxygen. When it is introduced into
the intake tract of an internal combustion engine, it is sucked
into the combustion chamber and, on the compression stroke, when
the charge air temperature reaches 565 deg, a very oxygen-rich
mixture results. If we add extra fuel during nitrous oxide
injection, the effect is like a super charger or increasing the
compression ratio of the engine. Automotive nitrous systems work
like the automotive equivalent of a jet's "afterburner" and is used
for short duration extra bursts of power.
Nitrous oxide has this effect because it has a higher percentage of
oxygen content than does the air in the atmosphere. Nitrous has 36%
oxygen by weight and the atmosphere has 23%. Additionally, nitrous
oxide is 50% more dense than air at the same pressure. Thus, a
cubic foot of nitrous oxide contains 2.3 times as much oxygen as a
cubic foot of air. Just do a bit of math in your head and you can
see if we substitute some nitrous oxide for some of the air going
into an engine than add the appropriate amount of additional fuel,
the engine is going to put out more power. 
