|
|
- Liquid nitrogen will condense oxygen from the air. This is most alarmingly
demonstrated if a person leaves his/her vacuum pump's coldfinger in a Dewar of liquid
nitrogen overnight. In the morning the coldfinger will contain
LIQUID OXYGEN up to the level of the nitrogen in the Dewar.
Liquid oxygen is a significantly more hazardous cryogen because if it's properties as a powerful oxidant.
|
|
- Guard against pressure build-up by using a pressure relief vessel or a venting lid.
|
- Remove metal jewelry/watches on hand and wrists.
|
- Glass Dewars must be taped solidly around the outside. The plastic mesh with which
some small thermoses are sold protects the Dewar itself to some extent, but does not protect
very well against injury from glass shards resulting from implosion.
|
- Use only vessels designed for extreme cold. Not all Dewars are rated for liquid
cryogens. Be especially careful that any equipment used for use with liquid oxygen is rated for oxygen use,
and is clean. Always follow manufacturers' guidelines for use of cryogen vessels of any
size.
|
- Do not carry liquid cryogens in a passenger elevator.
|
- Never work alone with hazards, always have at
minimum two people moving a large Dewar in hallways, elevators, and
outside of buildings.
|
- Cryotubes containing samples stored under liquid nitrogen may explode without warning.
Tube explosions are thought to be caused by liquid nitrogen entering the tube
through minute cracks and then expanding rapidly as the tube thaws. Serious
accidents have occurred around the country due to tube failures. A researcher in
California lost an eye; numerous others have suffered plastic shards embedded in their
hands and faces.
|
