What are the hazards of liquid nitrogen in a laboratory and which is most likely to cause a serious incident?
Of the three primary hazards associated with liquid nitrogen – cryogenic burns, asphyxiation, and pressure build-up – asphyxiation is statistically the most likely cause of serious injury or fatality in a laboratory setting. Liquid nitrogen is colourless, odourless, and produces no warning signal as it evaporates. A single 20-litre dewar emptying in an enclosed room with inadequate ventilation can reduce oxygen concentration below the HSE threshold of 19.5 per cent within minutes. Staff may lose consciousness before registering any symptoms.
Cryogenic contact burns are more immediately obvious but less frequently fatal. The greatest risk is hand and arm contact during routine dewar filling or sample retrieval, particularly when staff are not wearing appropriate cryogenic gloves and face protection. Pressure incidents occur most commonly with improvised or non-approved storage containers – all vessels used for liquid nitrogen storage must be rated and approved for cryogenic service. Fixed oxygen depletion monitors with audible alarms are a mandatory control measure in any room where liquid nitrogen is stored in quantities above approximately 50 litres. Contact Cryolab for a full PPE and safety equipment specification for your laboratory.
