Hello everyone, The reason for the fire alarm activation and building evacuation earlier today was that in a lab on 3rd floor (new wing) one of the valves on a liquid nitrogen (LN2) tank froze open and sent an uncontrolled volume of nitrogen (N2) into the room. Nitrogen is a known asphyxiant, and at the time when the researcher decided to activate the fire alarm there was a blanket of N2 vapor of about 1 ft. in the lab, and the valve could not be closed. EHS also responded to the incident, but by the time they arrived to the lab the LN2 tank had emptied and the ice around the hose and valves started to melt. The LN2 tank will need to be serviced and cleared for use by Indiana Oxygen before it can be used again. I recommend to visually inspect the valve on the LN2 tank EVERY TIME before planning on opening it to fill a dewar. Any sign of ice is an alarm that the valve might be frozen closed or might freeze open upon opening. Use a piece of cloth, or the heat gun to free the valve from any ice and make it safe to operate before using it. A note could be added to the tank to remind people I recommend adding a note on the LN2 tank, to remind users of this. Never use a wrench, or hammer, or any hard object to try to free a frozen valve on a LN2 tank. Instead, always use a warm cloth, or a heat gun to slowly warm up the valve and free it from ice. Thank you, Gabriela __________________ Gabriela Nagy, PhD Industrial Education Director Davidson School of Chemical Engineering Room FRNY G051 Purdue University Tel: (765)-496-1710 E-mail: nagyg@purdue.edu<mailto:nagyg@purdue.edu>