Air, nitrogen dioxide and oxygen are common oxidisers. If for example oxygen is not handled correctly, the surrounding atmosphere can become enriched with oxygen. The information here details the dangers of enrichment and the simple measures required to use oxygen safely.
Atmospheric gases are non-toxic. If their concentrations change, however, they can have an impact on life and combustion processes (especially in the case of oxygen). A sufficient amount of oxygen must be present in breathable atmospheres.
Oxygen itself is not flammable, but it does support combustion. Nitrogen and argon, however, inhibit combustion. Any changes in the concentration of these gases cannot be detected by human senses. If they are not handled correctly, accidents may occur.
In order to be stored as liquids, these gases have to be cooled to extremely low temperatures (less than -180 0C at atmospheric pressure). In this state, they can rapidly cause cold burns and make certain materials brittle, which in turn 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 on a number of factors including:
The concentration, temperature and pressure of reactants
Ignition energy and the mode of ignition.
Combustibility of materials
The risk of fire increases considerably when the concentration of oxygen in an atmosphere rises, even if it is just by a few percent. Sparks that under normal conditions would be harmless can cause fires in oxygen enriched atmospheres, and materials that would not normally burn in air - including fireproof materials - may burn vigorously or even spontaneously.
Hydrocarbon oil and grease
Oil and grease are particularly hazardous in the presence of pure 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 combustion accidents are triggered when cigarettes are lit in oxygen-enriched atmospheres. The risks of smoking in oxygen-enriched atmospheres or places where oxygen enrichment may occur are extremely high. Smoking must be forbidden in all such areas.