Cryogenic storage dewar is a vacuum-insulated vessel engineered to maintain biological or industrial materials at cryogenic temperatures, typically between minus 150 and minus 196 degrees Celsius, using liquid nitrogen as the refrigerant. Unlike a mechanical ultra-low temperature freezer, which uses a compressor-driven circuit to maintain temperatures around minus 80 degrees Celsius, a cryogenic storage dewar has absolutely no moving parts. It relies entirely on the evacuated space between its double walls to prevent heat ingress. This makes it immune to power cuts, mechanical failure, and compressor breakdown, and gives it a theoretical operational lifespan of many decades with proper maintenance.
The temperature difference between minus 80 and minus 196 degrees Celsius is not merely quantitative but qualitative in its biological significance. At minus 80 degrees Celsius, enzymatic activity and molecular degradation are dramatically slowed but continue at a measurable rate. At minus 196 degrees Celsius all biological and chemical processes cease entirely, allowing human embryos, gametes, stem cells, primary cell lines, and biological reference materials to be stored indefinitely without measurable degradation. This is why liquid nitrogen storage in a cryogenic dewar is the absolute gold standard for long-term biological preservation.
Modern cryogenic storage dewars are available in an enormous size range, from compact 1 to 5 litre units for short-term handling through to 500-litre floor-standing vessels with automated liquid nitrogen supply used in major biobanks. The most common sizes in UK clinical and research settings fall between 20 and 100 litres. Key specifications to compare when selecting a vessel include static evaporation rate, static hold time, canister configuration, neck diameter, and compatibility with continuous monitoring and alarm systems.
Vapour-phase capability has become a standard requirement in most new clinical dewar procurements. In vapour-phase storage, specimens are held above the liquid nitrogen surface in the cold nitrogen vapour zone rather than submerged in liquid. This eliminates any theoretical risk of cross-contamination between specimens through the liquid phase, a consideration particularly important in IVF clinics handling open vitrification carriers where human embryos and oocytes from different patients are stored in the same vessel.
For HFEA-regulated IVF clinics, every dewar must carry appropriate CE marking, be part of a documented quality management system, and be connected to a validated continuous monitoring and alarm infrastructure. Continuous monitoring with audible and visual alerts and out-of-hours escalation is expected practice and will be assessed at HFEA inspection.
Browse our certified range of cryogenic storage dewars for clinical, veterinary, and research use with UK-based technical support.
