A storage dewar is a vacuum-insulated vessel that holds liquid nitrogen at -195.8 degrees C, used in IVF clinics, sperm banks, and research laboratories to preserve biological samples for months or years without biological degradation. Named after Sir James Dewar who developed the vacuum flask principle in the 1890s, modern cryogenic dewars are precision-engineered to minimise LN2 evaporation and maintain stable internal temperatures over long periods.
How is a storage dewar different from a household vacuum flask?
The operating principle is the same – a vacuum between two walls prevents heat transfer – but the engineering tolerances, materials, and construction are entirely different. A laboratory storage dewar must maintain cryogenic temperatures continuously, often for years, with minimal maintenance. The vacuum quality, neck plug design, and internal canister system are all built to a specification that domestic products do not approach.
What size storage dewar does an IVF clinic need?
A clinic running 100 to 200 cycles per year typically manages with one or two working dewars of 20 to 35 litres, depending on sample retention periods. A licensed storage bank holding samples under the HFEA’s 55-year maximum storage framework – introduced under the Health and Care Act 2022 with consent renewed every 10 years – may require significantly larger capacity, often across multiple vessels with formal inventory management.
How should a storage dewar be maintained?
Keep the neck plug in place whenever the vessel is not being accessed. Check liquid nitrogen levels weekly as a minimum, or install continuous monitoring with an alarm. Inspect the neck and exterior for frosting that indicates abnormal heat ingress. A vessel that is warming faster than its rated evaporation suggests vacuum degradation and should be assessed before it fails in service.
A storage dewar with a failing vacuum can look identical to a functioning one from the outside. The only way to detect vacuum degradation early is consistent LN2 level monitoring – not visual inspection.
Cryolab supplies storage dewars for UK IVF clinics and research labs. See the CryoNest Series or contact the team.
