Dewar nitrogen storage refers to the use of vacuum-jacketed vessels – dewars – to hold liquid nitrogen and the biological samples immersed or suspended within it at -195.8 degrees C. This is the standard method for long-term cryogenic preservation of embryos, sperm, oocytes, and biological tissue in UK IVF clinics, sperm banks, and research laboratories. No other commercially viable method achieves the same combination of temperature stability, storage duration, and sample accessibility.

What are the practical day-to-day requirements of dewar nitrogen storage?

Liquid nitrogen evaporates continuously, so any dewar-based storage system requires a reliable LN2 supply and a regular top-up schedule. Labs need either bulk LN2 delivery with on-site storage, or a regular cylinder supply from a gas supplier. The top-up schedule should be based on the vessel’s rated static evaporation rate plus a safety buffer – never allow a vessel to drop below 25 to 30 percent capacity before refilling.

How should LN2 be safely added to a storage dewar?

Always use appropriate PPE when handling liquid nitrogen: cryogenic gloves rated for LN2 contact, a face shield, and a lab coat or cryogenic apron. Pour slowly to minimise splashing and boil-off. Never seal a dewar immediately after filling – allow the initial boil-off to subside before replacing the neck plug. Ensure the room is adequately ventilated given the HSE oxygen depletion threshold of 19.5%.

What records should be kept for dewar nitrogen storage in a licensed facility?

HFEA-licensed fertility clinics must maintain records of all stored samples, storage locations, LN2 level checks, top-up events, and any incidents involving storage vessels. The records form part of the traceability chain that the HFEA inspects. Research institutions without HFEA licensing should apply the same standard as a matter of good practice and risk management.

Dewar nitrogen storage looks simple from the outside. The vessel sits there, the LN2 evaporates slowly, and the samples stay frozen. What you do not see is the inventory system, the monitoring schedule, and the emergency protocol that makes that simplicity reliable.

Cryolab supplies storage dewars, LN2 handling equipment, and safety wear for UK laboratories. View the full range or contact the team.