Barb,

If there's a problem with the liquid nitrogen delivery system, then nitrogen will leak into the room and the oxygen will be displaced; and people need oxygen. 

Calibrate the oxygen sensor with calibration gasses (like an oxygen/nitrogen mixture).  We use two calibrators, 17% oxygen and 20.9% oxygen.  And the unit calibrates just like a pH meter. 

Here are a couple of tips to be aware of.  Apparently nitrogen asphyxiation does not cause a physiological panic/struggle like carbon dioxide asphyxiation does.  So if the sensor alarms, verify that it's a positive or negative alarm with a calibrator gas so you know if you really have a problem.  The sensors we use for those units last about a year and tend to go flakey toward the end of their service lives.  So you might want to install a switch to silence a false alarm; if you can't silence a false alarm, then you'll definitely need to consider hearing PPE. 

Eric

Eric Clark

Safety & Compliance Officer

Los Angeles County Public Health Lab

>>> On 8/29/2012 at  7:01 AM, in message <205AAA7AEFEF49ADB5CC346CB5D4985F**At_Symbol_Here**owu.prv>, <bjwiehe**At_Symbol_Here**OWU.EDU> wrote:

We are installing an Oxygen Sensor in a room using Liquid Nitrogen.  Question, why do you mount it in the room where loss of Oxygen would be present?  What type of training should the technician have overseeing the monitor?(ie respirator fit)

Barb Wiehe