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There have been two separate incidents here at the University involving liquid nitrogen (LN2). The first incident involved a student who was provided incorrect gloves for dermal protection against liquid nitrogen and experienced an exposure on his finger. The gloves he was wearing were for hot temperature processes and made from a cloth material. A small quantity of liquid nitrogen spilled on his hand during a dewar filling process and it penetrated the glove causing frostbite on one of his fingers. The cloth glove actually made the situation worse by allowing the liquid through the material and holding it to the skin.
Please note there are two types of gloves that can be used to work with or around LN2. One is a cryogenic glove. This is an insulated glove that provides protection from both the liquid as well as the extreme temperatures. The second type of glove is a thick, all leather glove that provides incidental splash contact protection only. This glove does not provide protection from the extreme cold temperatures. For specific vendor information please contact DEHS at x8475.
The second incident involved two graduate students who were filling a small dewar from the main, high pressure LN2 filling line (which has a pressure of approximately 100 PSI). The main line pressure was too great for the small dewar and the filling hose detached from the small dewar, spewing LN2 all over the filling room. The combination of the main line pressure and the stainless steel mesh hose (weighing about 10 lbs) can be a very dangerous situation. Additionally, LN2 expands about 700 times when it changes from a liquid to a gas, thus oxygen displacement can rapidly take place. The two students immediately exited the area and contacted departmental personnel to turn off the main line valve on the exterior of the building.
Small dewars should only be filled using the larger, 160 ltr dewar because the pressure is sufficiently low (approximately 10-22 PSI) to eliminate the potential for hose detachment. Never fill the small dewars from the bulk, high pressure tanks.