Cryogenic Safety
Refrigerators and freezers An explosion-proof fridge must be used for chemicals. Do not use your refrigerator or freezer as a dump. Make sure everything you put in is tightly sealed in a way that will not leak when cold. Check the contents frequently and discard unwanted samples. Food must never be stored in a refrigerator used for chemicals.
Liquid N2/ Solid CO2

These substances can freeze-burn you. Equipment cooled outside by liquid N2 but open to air will allow liquid O2 to form inside which can create a dangerous pressure rise on warming or an explosion with flammable material. Use liquid nitrogen to cool sealed or evacuated systems only. 

In closed environments, these chemicals can cause asphyxiation. Therefore, be aware of the dangers when transporting in lifts. To avoid in possible risks from nitrogen boil off during, for example, a prolonged period of lift breakdown, Dewars of liquid nitrogen must not be accompanied in lifts. Rather, two people should be assigned to transport the Dewars, one to load and one to receive at the destination floor. To prevent others from entering the lift, fitted straps should be pulled across the entrance. Dry ice should be transported in a thermally insulated container with a loose-fitting lid. Do not use am airtight container as the gaseous CO2 is likely to cause the container to explode. A block of dry ice (~ 1 kg) when completely sublimed is enough to reduce the oxygen level in a stalled lift to suffocation level. Use the stairs whenever possible.

See http://www.chemistry.nus.edu.sg/PSSO/safety/risk/cryogenic.htm for handling, transportation and storage of liquid nitrogen.

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