One of the reasons that liquid nitrogen is an asphyxiation hazard is that it has an approximately 700-1 expansion factor. This means that one liter of liquid nitrogen becomes 700 liters of gas. Therefore, a small spill can quickly displace the air in a room. It does not have a significant density difference from atmospheric air (which is already about 80% nitrogen), so it will not collect on the floor or rise to the ceiling. Sensors should be placed at approximately the level of people in the room--if users are usually standing, then the sensors should be placed at "head" height.
We did a quick calculation to convince our researchers not to put dewars of LN2 in their vehicles--a small (3 L) dewar, if spilled, can easily displace the air in an average sedan to below 15%, which means almost instant asphyxiation and a vehicle crash. It's nice to give facts beyond "you're not supposed to."
Thank you for your responses.
Neal, fair enough put the red flags away...I was thinking scuba but it isn't going to fly with anyone here to go to that extent.
I appreciate getting feedback from your perspectives rather than push back from others.
-- ----------------------------------- Emily Reiter Lab Coordinator/Safety Coordinator Dept of Chemistry and Biochemistry University of Alaska Fairbanks 192 Reichardt Bldg (907) 474-6748
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