By Jack Ori
Updated March 24, 2022
Oxygen is the life‑supporting gas in the air, but when it is distilled and cooled to cryogenic temperatures, it turns into a liquid. Liquid oxygen (LOX) is used in rocket engines, certain medical applications, and, though rarely, in some explosive formulations. Its extreme cold and high concentration make it a powerful oxidizer that can turn ordinary organic materials into fire‑hazards.
Liquid oxygen is oxygen that has been extracted from air and then cooled below its boiling point of −183 °C (according to Harvard University). It is stored in insulated tanks to keep it from evaporating. While it is not flammable on its own, LOX dramatically accelerates the combustion of other materials.
Because LOX is a highly concentrated oxidizer, it can quickly transform a combustible surface into an explosive one. In practice, it is often mixed with other gases to stabilize it before use in propulsion systems.
When liquid oxygen contacts asphalt—a composite of hydrocarbons and organic additives—it infiltrates the material, creating an oxygen‑rich environment. If vehicles passing over the contaminated surface leak oil or grease, the combination can ignite instantly or even cause a massive detonation.
Upon spilling, LOX vaporizes in the ambient air, forming a dense cloud of concentrated oxygen. This cloud can soak into clothing or organic matter, dramatically increasing the rate of combustion. A person exposed to such a cloud could ignite a cigarette or other ignition source within seconds. Vehicles driving over asphalt saturated with LOX can trigger an explosion due to the sudden combustion of the oxygen‑rich pavement.
• If you come into contact with liquid oxygen, move to an open, well‑ventilated area immediately and allow your clothing to dry. Avoid any ignition sources for at least 15 minutes.
• If LOX spills on asphalt, cordon off the area for a minimum of 30 minutes and prohibit pedestrian or vehicular traffic. Report the incident to emergency responders for a thorough assessment.
