A Risk Assessment of Oxygen Gas
We live in an environment that contains a mixture of gases called air which is about 78% nitrogen, 21% oxygen, and 1% argon. Air is familiar to us because we interact with air constantly so we understand the behaviors of materials, flames, and reactions in air. However, when dealing with oxygen that is concentrated above 21%, the behavior of the atmosphere changes. As such, it is important to understand the risks associated with compressed oxygen gas, the greatest of which is the increased combustibility of everything in an enriched oxygen environment.
Fire Hazards Associated with High Oxygen Concentration
Oxygen gas itself is not flammable, but it does encourage combustion meaning that in an oxygen-heavy atmosphere things burn more readily. Things that normally do not burn in air such as flame-retardant clothing and fireproof materials will catch fire in an enriched oxygen environment. Hydrocarbon-rich substances including fuels, oils, and greases present a particularly high fire incidence because they will burn spontaneously in oxygen.
Anyone working in a high oxygen atmosphere should be aware of the fire hazards and take steps to mitigate the risk. Fireproof clothing should only be considered safe if it has been tested in a high oxygen environment. Also, clothing should not be loose but should be easy to take off in the event of a fire. Additionally, equipment used to store and dispense concentrated oxygen should be free of lubricants, grease, and oil (this also applies to clothing and work pieces). Only oxygen-specific lubricants should be used on valves and tubes of tanks containing compressed oxygen gas.
Precautions and Prevention of Fires
The best way to prevent a fire when working with compressed oxygen is to prevent leakage of the gas from the tank. Proper inspection should be performed on all equipment before it is approved for use, including tubes, pipes, valves, tanks, torches, and tips. Following proper handling and storage techniques is also important to prevent damage to the cylinders. In the event that a leak is found, inform your supplier immediately so that they can send a qualified professional to deal with the issue.
As with all compressed gases, a well-ventilated work area will help to prevent a dangerous accumulation of oxygen. Whenever the oxygen is not in use, the valve should be shut on the oxygen bottle to prevent leakage while work is not being performed. After working in an oxygen-rich atmosphere, workers must air out their clothing as it may hold residual oxygen that is a fire risk even after leaving the workspace.
All oxygen enriched atmospheres should have fire extinguishers and/or hoses available to douse possible flames as these are the best for dealing with oxygen-induced fires. Finally, smoking and open flames must be prohibited and electricity closely monitored in and nearby oxygen-rich environments.
The best way to prevent a fire in an oxygen-rich atmosphere is to protect against leakage. Due to the high risk of combustion, precautions should be taken to ensure a safe workspace and a successful welding or cutting project.
