Common oxidizers include air, nitrogen dioxide and oxygen. Oxygen enrichment can arise when using oxygen unless good practice is observed. This information specifies the dangers involved and the simple precautions to be taken to ensure that every user can employ oxygen with confidence and without danger.
Atmospheric gases are non-toxic, but alterations in their concentrations - especially that of oxygen - have an effect upon life and combustion processes. It is essential to have sufficient oxygen in atmospheres being breathed.
Although not flammable in itself, oxygen does support combustion while nitrogen and argon inhibit combustion. If good practice is not observed accidents may happen because changes in concentration cannot be detected by people.
When these gases are in their liquid state, it is necessary to bear in mind the extremely low temperature involved (less than -180 oC at atmospheric pressure). They can rapidly cause cold burns and make certain materials sufficiently brittle, which may lead to structural failure.
Fire hazards from oxygen enrichment
Oxygen reacts with most elements. The initiation, speed, vigour and extent of these reactions depend in particular upon:
The concentration, temperature and pressure of the reactants
Ignition energy and mode of ignition.
Combustibility of materials
Oxygen enrichment of the atmosphere, even by a few percent, considerably increases the risk of fire. Sparks which would normally be regarded as harmless can cause fires, and materials which do not burn in air, including fireproofing materials, may burn vigorously or even spontaneously in enriched air.
Hydrocarbon oil and grease
Oil and grease are particularly hazardous in the presence of oxygen as they can ignite spontaneously and burn with explosive violence. They should never be used to lubricate oxygen or enriched-air equipment (special lubricants which are compatible with oxygen can be used under certain conditions).
Many burning accidents are triggered off by the lighting of a cigarette, making it impossible to over-emphasize the danger of smoking in oxygen-enriched atmospheres or in places where oxygen enrichment may occur. Smoking must be forbidden in all such areas.
