Keeping oxygen content at safe level in encl- - osure cooled cryogenically

摘要

Oxygen content is kept above a preset level in the atmosphere of a non-open closure cooled by the injection and vaporisation of at least one cryogenic liquid which cannot sustain life but can be breathed as a gas. Simultaneously with the injection of cryogenic liquid(s), a gas mixture containing O2 is blown in: pref. at ambient temp., and comprising atmospheric air, the cryogenic liquid is N2.