Liquid Oxygen – Fire Hazards of Oxygen and Oxygen-Enriched Atmospheres

Oxygen, which is essential to life, is not flammable in itself but supports and accelerates combustion. The normal concentration in the air that we breathe is approximately 21% by volume. Most materials burn fiercely in oxygen; the reaction could even be explosive. As the oxygen concentration in air increases the potential fire risk increases. Being heavier than air, oxygen can accumulate in low lying areas such as pits, trenches or underground rooms. This is particularly relevant when liquid oxygen spills out. In that case the generated cold gaseous oxygen is three times heavier than air. As 1 l of liquid oxygen liberates circa 850 l of gas, the phenomenon of oxygen enrichment is massively amplified by a spill of liquid oxygen, and thus fire risk is increased.