A dry shipper is a specialist cryogenic transport vessel designed to carry biological samples at ultra-low temperatures without containing any free liquid nitrogen. This single characteristic is what makes it the gold standard for transporting frozen embryos, sperm, oocytes, semen straws, and other cryopreserved biological material anywhere in the world.
Unlike a standard liquid nitrogen dewar, which holds liquid nitrogen in a free pool, a dry shipper works by absorbing liquid nitrogen into a highly porous absorbent material, usually a specially engineered aluminium matrix, built into the inner wall of the vessel. When the dry shipper is charged, liquid nitrogen is poured in and left to soak fully into this matrix. Once the matrix is saturated, any excess free liquid is poured away. What remains is nitrogen locked into the absorbent core, which evaporates slowly and continuously over the transport period, maintaining the internal vapour temperature well below minus 150 degrees Celsius throughout.
Because there is no free liquid present, the vessel is safe to tip, tilt, or handle without risk of nitrogen spilling. This is what allows dry shippers to be transported by road courier, air freight, or hand-carried on commercial flights without triggering the dangerous goods restrictions that apply to vessels containing free cryogenic liquid.
The internal temperature of a charged dry shipper is maintained by the slow release of absorbed nitrogen vapour. Depending on the model, the hold time, meaning the number of hours or days the vessel can maintain cryogenic temperatures after charging, ranges from around 24 hours for smaller or entry-level units to well over 72 hours for high-specification units. For domestic UK transport, even a basic dry shipper provides a very generous safety margin. For international shipments involving multiple flights and potential customs delays, a longer hold time model is essential.
Dry shippers are used across a wide range of sectors in the UK and internationally, including human fertility clinics transporting embryos and gametes between HFEA-licensed facilities, veterinary reproduction centres moving equine, bovine, and canine semen or embryos, research laboratories shipping cell lines and tissue samples, and biobanks transferring cryopreserved material between storage sites.
Choosing the right dry shipper comes down to matching the hold time, internal capacity, and physical dimensions of the unit to your specific transport requirements. Cryolab stocks a full range of dry shippers from 2 litres to 10 litres, covering every use case from single-sample clinical transport to high-volume research shipments. Browse the full CryoStork dry shipper range at Cryolab.
