A standard cryogenic dewar and a dry shipper both maintain samples at cryogenic temperatures using liquid nitrogen, but they do so in fundamentally different ways and are designed for different purposes.
A standard dewar for long-term IVF storage contains free liquid nitrogen. Samples are stored in the liquid or just above it in the vapour space. The dewar is filled periodically as nitrogen evaporates. It is designed for static use in a fixed laboratory location and is not appropriate for most transport applications because the free liquid nitrogen presents a spill risk and is subject to transport hazard classifications.
A dry shipper contains no free liquid nitrogen. Instead, it has an absorbent matrix built into its inner walls that soaks up liquid nitrogen during charging. After charging, the excess free liquid is poured out, leaving only absorbed nitrogen. During use, this absorbed nitrogen slowly evaporates, maintaining the internal temperature at cryogenic levels. The absence of free liquid means it can be safely transported by road courier.
The practical distinction is straightforward. Use a standard dewar for long-term laboratory storage. Use a dry shipper when samples need to move.
Dry shippers typically have shorter hold times than standard dewars. A standard 35-litre dewar may hold enough nitrogen for weeks or months. A dry shipper maintains cryogenic temperatures for 24 to 72 hours.
Cryolab supplies both long-term storage dewars and dry shippers for UK fertility clinics. Visit cryolab.co.uk“>Cryolab
