Vial explosion by warming LN2
Title
Vial Explosion by Warming LN2
Monday, June 3, 2019
Situation
The researcher was cryo-fracturing a sponge-like material (99% porosity) by first submerging the sample in liquid nitrogen, then tearing it apart using two pairs of tweezers. When finished the sample was transferred into a scintillation vial for storage. Because of the high porosity, an estimated amount of 1 cm^3 LN2 was absorbed in the sponge-like material, and was also transferred to the vial. The researcher then made a mistake by capping the vial because the researcher wasn't paying too much attention while talking to a lab-mate. Soon after capping the vial, the vial exploded in their hand because of the volume expansion of the nitrogen gas. Fortunately, the researcher was all geared up (gloves, goggles and lab-coat) so there were just a couple of scratches on their hand. The coworkers in the lab quickly located gauze pads and bandages for the researcher, and the bleeding was stopped very soon.
Suggestions
(1) Do not be in a rush to put any samples that were just submerged in liquid nitrogen in a sealed container wait a minimum of 24 hours for vapors to expand or LN2 liquid to drain out if still in the vapor phase. LN2 expands 600x in volume when warmed so very little amount of liquid nitrogen in a sealed environment could be devastating.
(2) Be on your toes when preparing samples using cryo-fracturing. Avoid any distractions during lab work and focus your attention completely on your work.
(3) Always fully gear up and never work alone in the lab. Add a blast shield and stay away while thawing. Or use a face shield with goggles and cut resistant gloves when handling materials that have not thawed. It is also recommended to perform cryo-fracturing in a fume hood. It won't just be minor scratches if the researcher was working without any protection on a weekend.
(4) A first report of injury should be completed for even minor injuries and exposures.
