Cryogenic storage dewar

Cryogenic storage dewars can range widely in size and may take several different forms, including open buckets, flasks with loose-fitting stoppers, and self-pressurising tanks.

Dewars are also designed to be resistant to any sort of puncture to preserve the contents, as cryogens are costly to produce, and some (like helium) are in limited global supply.

Firstly, no dewar can provide perfect thermal insulation and the cryogenic liquid slowly boils away, which yields an enormous quantity of gas.

[3] Secondly, if a dewar is left open to the air for extended periods, atmospheric chemicals can condense or freeze on contact with the cryogenic material.

Thirdly, the gas escaping from a dewar can gradually displace the oxygen from the air in the surrounding area, which presents an asphyxiation hazard.