Dewar Precautions
Always handle glass dewars with care. Any product incorporating a vacuum is a potential safety hazard and should be treated with caution. If in doubt, contact your safety officer. |
When handling dewars containing liquefied gases or cryogenic liquids:
- Wear protective equipment:
- goggles or face shield
- an insulated or rubber apron
- insulated gloves
- When pouring liquefied gases from one container to another:
- cool the receiving container gradually to minimize thermal shock
- pour the liquified gas slowly to prevent splashing
- vent the receiving container to the atmosphere
For glass dewars
- Use a plastic stirring rod when stirring substances in a dewar containing liquefied gases (or other materials of extremely low temperature). Do not use a glass or metal stirring rod unless it has a protective coating.
- Do not handle heavy objects above the dewar. If unavoidable, place a protective cover over the dewar opening. If an object of sufficient weight is accidentally dropped into the dewar, shattering may occur.
- If the dewar has a protective mesh covering, do not remove it. This cover minimizes the risk of flying particles should the dewar be knocked over, dropped, or broken.
Check the Cryogen Level
If performing an analysis that requires use of the cold trap and cryogen, check the cryogen level in the dewar. It should be about 25 mm (1 in.) from the top.
The cryogen must not be cold enough to trap the carrier gas or analysis gas. Do not use liquid nitrogen with argon carrier gas. For example, use an alcohol and liquid nitrogen slurry (-80 ºC). |
Use appropriate safety procedures when handling all cryogens. Be sure to wear safety glasses and gloves, and observe the precautions listed earlier. |
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