Department of

Environmental Health and Safety

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Liquid Nitrogen

Dangers of Transporting Liquid Nitrogen

Liquid nitrogen is commonly transported on our campus in large vacuum flasks called Dewars. Among the largest of these are 160 vessels just over five feet tall, which maintain a slight internal pressure and continually vent to the atmosphere as the nitrogen slowly boils off. The expansion ratio is 710:1 between the gas and liquid phases. Sometimes recently filled cylinders will vigorously off-gas. Any venting can be a significant potential hazard if you are in an elevator, or any enclosed or confined space, as the nitrogen can displace the oxygen, causing asphyxiation. Recently a researcher was transporting a 160-liter pressurized container between floors when the elevator stalled. After a response from the Fire Department, EHS, and an elevator technician, the researcher left the elevator safely, but this could have been a close call, or worse.

DO NOT EVER transport a pressurized container of Liquid Nitrogen or Cryogenic Material on an elevator with any person in the elevator! When a pressurized container of liquid nitrogen or other cryogen must be transported in an elevator, the elevator must travel between floors unoccupied. Personnel must be stationed at all “in-between” floors to prevent riders from entering the elevator. The sender is to remain outside the elevator and activate it to the desired floor. Another person is to be available on the receiving floor to take the liquid container off the elevator at its destination.

For assistance in establishing safe handling practices for cryogens, please contact EHS – 581-6590.