Oxygen hazards are often overlooked when installing and using electrolysis systems. All fuels are more flammable and easier to ignite in oxygen-enriched atmospheres. Bulk materials that are not considered flammable in air environments may be readily available fuel sources in oxygen, especially in a pressurized environment. Oxygen fires that do not involve the hydrogen side of the electrolyzer have occurred. Material selection and cleanliness for oxygen service are important considerations for electrolyzer manufacturers and users, especially if oxygen is compressed and stored for downstream use. Secondary effects, including fire spread with involved oxygen, should be considered during integrated system hazards analyses.
The outlet location for the oxygen gas stream should be considered carefully, especially for large electrolysis systems. Vent outlets should be free from ignition sources and located at a safe distance from the hydrogen vent outlet and building air intakes.
For indoor applications, if oxygen is released into the electrolyzer room, sufficient ventilation should be provided to prevent oxygen-enriched atmospheres above 23.5%. If oxygen is stored, mitigation strategies for hydrogen cross-over should be used. Never store a flammable mixture of oxygen and hydrogen.