Liquid Nitrogen and Frozen Biological Material
When ampoules are submerged in nitrogen, the pressure difference between the outside and inside of the ampoule is high; if it is not perfectly sealed, liquid nitrogen will enter, so that when thawed the ampoule will explode violently. Ensure that ampoules are perfectly sealed, but in any event always wear eye protection and a face shield. Thawing from storage under liquid nitrogen must always be allowed to occur in a container with a lid, such as a plastic bucket, and eye protection and a face shield must be worn.
Ampoules in liquid nitrogen can explode when they are removed from the dewar or when thawed. Only trained individuals wearing appropriate personal protective equipment should work with liquid nitrogen.
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