What pressure does liquid nitrogen exert in storage vessels and why does pressure management matter for laboratory safety?
Liquid nitrogen stored in an open-mouth dewar at atmospheric pressure boils at -195.8°C and exerts no significant internal pressure beyond atmospheric. The pressure risk arises specifically with sealed or pressurised vessels – including liquid nitrogen cylinders, pressurised dewars used for dispensing, and any container that is sealed while containing liquid nitrogen or cold vapour. As liquid nitrogen warms and vaporises, it expands at a ratio of approximately 694 to 1 – meaning one litre of liquid nitrogen produces 694 litres of gaseous nitrogen at room temperature. In a sealed container, this expansion generates pressure rapidly, creating an explosion hazard if pressure relief mechanisms are absent or fail.
Standard biological storage dewars used in IVF laboratories are open-neck vessels specifically designed to vent nitrogen vapour rather than build pressure. They must never be sealed with airtight lids. Pressurised dispensing cylinders, used for controlled liquid nitrogen transfer to smaller vessels, are engineered with calibrated pressure relief valves and require specific handling training. Cryolab supplies open-neck storage dewars and liquid nitrogen dispensing systems with appropriate pressure management for laboratory use. All staff handling pressurised liquid nitrogen equipment should wear full cryogenic PPE. Contact us for guidance on safe dispensing equipment for your facility.
