Oxygen compatibility

Oxygen compatibility is the issue of compatibility of materials for service in high concentrations of oxygen. It is a critical issue in space, aircraft, medical, underwater diving and industrial applications. Aspects include effects of increased oxygen concentration on the ignition and burning of materials and components exposed to these concentrations in service.

Understanding of fire hazards is necessary when designing, operating, and maintaining oxygen systems so that fires can be prevented. Ignition risks can be minimized by controlling heat sources and using materials that will not ignite or will not support burning in the applicable environment. Some materials are more susceptible to ignition in oxygen-rich environments, and compatibility should be assessed before a component is introduced into an oxygen system.

The issues of cleaning and design are closely related to the compatibility of materials for safety and durability in oxygen service.

Fires occur when oxygen, fuel, and heat energy combine in a self-sustaining chemical reaction. In an oxygen system the presence of oxygen is implied, and in a sufficiently high partial pressure of oxygen, most materials can be considered fuel. Potential ignition sources are present in almost all oxygen systems, but fire hazards can be mitigated by controlling the risk factors associated with the oxygen, fuel, or heat, which can limit the tendency for a chemical reaction to occur.

Materials are easier to ignite and burn more readily as oxygen pressure or concentration increase. so operating oxygen systems at the lowest practicable pressure and concentration may be enough to avoid ignition and burning.

Use of materials which are inherently more difficult to ignite or are resistant to sustained burning, or which release less energy when they burn, can, in some cases, eliminate the possibility of fire or minimize the damage caused by a fire.

Although heat sources may be inherent in the operation of an oxygen system, initiation of the chemical reaction between the system materials and oxygen can be limited by controlling the ability of those heat sources to cause ignition. Design features which can limit or dissipate the heat generated to keep temperatures below the ignition temperatures of the system materials will prevent ignition.

An oxygen system should also be protected from external heat sources.

The process of assessment of oxygen compatibility would generally include the following stages:

Compatibility analysis would also consider the history of use of the component or material in similar conditions, or of a similar component.

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