What Happened?

A student sustained injuries to both hands when a cryovial ruptured between their palms. The student was retrieving cryovials from a liquid nitrogen freezer in preparation for an experiment. As part of his routine, he thawed the cryovials by rolling them between his hands for a few seconds before transferring them to a 37 °C water bath. During this process, one of the cryovials ruptured forcefully. The student was wearing appropriate PPE at the time of the incident.

The student immediately reported to the Occupational Health and Safety Facility, where he was diagnosed with first-degree burns to both hands. The treating physician submerged his hands in warm water, applied lidocaine, and dressed the wounds. The student was released the same day and reported the incident to their PI that day.

What Was The Cause?

• Immediate cause: A cryovial stored in liquid-phase LN₂ pressurized during hand-rolling as trapped LN₂ vaporized; the vial ruptured between the student's palms, producing bilateral first-degree burns.
• Underlying causes:
  • Liquid-phase LN₂ storage permits ingress of LN₂ into cryovials over time; this is a known property of the storage method.
  • Hand-rolling was used as the initial thawing technique, placing both hands in the rupture path and accelerating vaporization.
  • No thawing shield or containment was used during warming.
  • PPE in use (cryogenic gloves, eye protection) was not designed to contain a pressurized rupture.
  • The lab's SOP and training did not identify hand-rolling as prohibited or rupture as a recognized hazard.
• Root causes:
  • Storage-mode hazard accepted without compensating controls. The lab uses liquid-phase LN₂ storage (a mode known to permit cryovial pressurization) without the compensating administrative and engineering controls that make this mode safe — specifically, a prohibition on hand-rolling, a requirement for shielded thawing, and face protection during warming.
  • Incomplete hazard model for LN₂ work. The lab's training and SOPs appear to cover cold-contact hazards (cryogenic gloves, thermal protection) but not the full set of LN₂ hazards: cold contact, pressurized rupture, and potential oxygen displacement. 

How Can Incidents Like This Be Prevented?

• No hand-rolling, ever. Cryovials retrieved from LN₂ can rupture during warming. Use an enclosed 37 °C water bath behind a shield, a dry thawing device, or a secondary-containment warming method.
• Thaw behind a shield, with a face shield on. A benchtop shield contains rupture fragments; a face shield protects the eyes and face.
• Consider vapor-phase storage. The single most effective step against both LN₂ hazards — cold burn and rupture. Evaluate at the lab or institutional level.
• Face shield + cryogenic gloves + long coat + closed shoes for every LN₂ interaction. No exposed skin at wrist, neck, or lower leg.
• Cold burns and ruptures are both delayed-presentation and surprise hazards. Any burning, tingling, numbness, or rupture should trigger an immediate visit to Occupational Health.
• Response model: the student in this case did everything right after the injury. Immediate OHS, appropriate treatment, same-day PI reporting. That's the template.