From: Emily Reiter <eareiter**At_Symbol_Here**ALASKA.EDU>
Subject: Re: [DCHAS-L] Oxygen Sensor
Date: August 29, 2012 2:23:56 PM EDT
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <CACO1vYPOGeVebQnnNFYgyUTXJSZ8SrHk4BY-FqR_BCTcSKmRSw**At_Symbol_Here**>

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."

On 8/29/2012 9:23 AM, Barbara Wiehe wrote:
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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