Safety
Vacuum flasks are at risk of implosion hazard and glass vessels under vacuum in particular may shatter unexpectedly. Chips, scratches or cracks can be a starting point for dangerous vessel failure, especially when the vessel temperature changes rapidly (when hot or cold liquid is added). Proper preparation of the Dewar vacuum flask by tempering prior to use is advised to maintain and optimize the functioning of the unit. Glass vacuum flasks are usually fitted into a metal base with the cylinder contained in or coated with mesh, aluminum or plastic to aid in handling, protect from physical damage and to contain fragments should they break.
In addition, cryogenic storage dewars are usually pressurized and may explode if pressure relief valves are not used.
Read more about this topic: Thermos
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