Safety
Since the liquid to gas expansion ratio of nitrogen is 1:694 at 20 °C (68 °F), a tremendous amount of force can be generated if liquid nitrogen is rapidly vaporized. In an incident in 2006 at Texas A&M University, the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed. As a result of the subsequent pressure buildup, the tank failed catastrophically and exploded. The force of the explosion was sufficient to propel the tank through the ceiling immediately above it.
Because of its extremely low temperature, careless handling of liquid nitrogen may result in cold burns.
As liquid nitrogen evaporates it will reduce the oxygen concentration in the air and might act as an asphyxiant, especially in confined spaces. Nitrogen is odorless, colorless and tasteless, and may produce asphyxia without any sensation or prior warning. A laboratory assistant died in Scotland in 1999, apparently from asphyxiation caused by liquid nitrogen spilled in a basement storage room. In 2012, a young woman in England had her stomach removed after ingesting a cocktail made with liquid nitrogen.
Oxygen sensors are sometimes used as a safety precaution when working with liquid nitrogen to alert workers of gas spills into a confined space.
Vessels containing liquid nitrogen can condense oxygen from air. The liquid in such a vessel becomes increasingly enriched in oxygen (boiling point 90 K; −183 °C; −298 °F) as the nitrogen evaporates, and can cause violent oxidation of organic material.
Read more about this topic: Liquid Nitrogen
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