Liquid Nitrogen Safety

http://engineering.dartmouth.edu/microengineering/ln2.html

Properties of Liquid Nitrogen (LN2)

  1. It is extremely cold: 77.3K = -196C = -320F at atmospheric pressure. This can cause severe frost bite.
  2. On vaporization it expands by a factor of 700; one liter of liquid nitrogen becomes 24.6 cubic feet of nitrogen gas. This can cause explosion of a sealed container, or it can displace oxygen in the room and cause suffocation without warning.
  3. It can become oxygen enriched and cause ordinarily noncombustible materials to burn rapidly.

Precautions when handling liquid nitrogen

  1. Treat liquid nitrogen and any object cooled with liquid nitrogen with respect.
  2. Take care not to allow liquid nitrogen to be trapped in clothing near the skin.
  3. Wear safety glasses or a face shield when transfering liquid nitrogen.
  4. Wear gloves when touching any object cooled by liquid nitrogen. Gloves should be loose fitting, so they could be thrown off if liquid were to pour inside them
  5. Use only approved unsealed containers. Never pour it into a coffee thermos. Never seal it in any container (it will explode).
  6. Never dip a hollow tube into liquid nitrogen; it may spurt liquid.
  7. Never use in a small poorly ventilated room, and never dispose of liquid nitrogen by pouring it on the floor. It could displace enough oxygen to cause suffocation. Nitrogen gas is colorless and odorless--the cloud that forms when you pour liquid nitrogen is condensed water vapor from the air, not nitrogen gas.
  8. Do not store liquid nitrogen for long periods in an uncovered container (on the other hand, never totally seal a container). Because the boiling point of oxygen, 90.1K, is above that of nitrogen, oxygen can condense from the air into the liquid nitrogen. If the air over the nitrogen circulates, this liquid oxygen can build up to levels which may cause violent reactions with organic materials; even materials which are ordinarily nonflammable. For example, a severe clothing fire could result from ignition in the presence of liquid oxygen.

First Aid

The above is first aid information is from the publication "Handle With Care", C 1996 Harsco Corporation, Factory code 7950-8052.
See also: How to Suffocate in a Cold Room

Christopher.G.Levey[AT]dartmouth.edu