Freezers, Laboratory, Cryogenic, Vapor Phase Nitrogen
Definition : Freezers that use liquid nitrogen as the cooling agent and vapor phase nitrogen for storage. Vapor phase nitrogen storage provides a temperature of -140 degrees Celsius (-220 degrees Fahrenheit) that is not as low as liquid nitrogen (-180 degrees Celsius [-292 degrees Fahrenheit]), but decreases the risk of cross-contamination among the stored products compared to freezers using liquid nitrogen immersion. These freezers typically consist of a chamber with two vessels separated by a vacuum space (the inner vessel for the cryogenic fluid and the outer vessel intended to insulate the cryogenic liquid from the environment); automatic level and cryogenic temperature controls; an external container to replenish the cryogenic fluid; a pressure-relief device; and a pressure-control valve. Cells and/or tissues are immersed in the vapor atmosphere above the liquid nitrogen in appropriate containers. Vapor phase nitrogen cryogenic laboratory freezers are used mainly for cell and/or tissue (e.g., ovum, embryo, bone, cornea) storage for extended time periods (typically several years).
Entry Terms : "Vapor Phase Nitrogen Cryogenic Freezers"
UMDC code : 22074