Just about everyone has heard a story about a cryotube exploding after being removed from storage. Do not end up being the source of the story with an unfortunate injury resulting from an exploding cryotube.
When liquid nitrogen finds its way into a cryotube from a small crack or improperly sealed top, it rapidly expands when removed from storage. Liquid nitrogen expands almost 700 times when vaporized. If this occurs inside a cryotube, the pressure is too much for the cryotube to withstand, and it explodes.
The tubes used for cryostorage must be specifically designed for the intended purpose. When removing cryotubes from storage, safety glasses, a face shield, heavy gloves, and a buttoned lab coat should be worn. During thawing, the tubes should be handled with added precautions, such as thawing them behind a safety shield or in a heavy walled container. In addition, the cryotubes are supposed to be stored in the gas phase, not the liquid nitrogen. So if they have fallen into the liquid nitrogen, added precautions should be taken.
Make sure all lab employees are aware of the hazards associated with cryogenics and they know to beware of exploding tubes!