From: Barbara Wiehe <bjwiehe**At_Symbol_Here**OWU.EDU>
Subject: Re: [DCHAS-L] Oxygen Sensor
Date: August 29, 2012 1:23:01 PM EDT
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <028e01cd8605$b7d01bc0$27705340$**At_Symbol_Here**>

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.


On Wed, Aug 29, 2012 at 12:45 PM, Neal Langerman <neal**At_Symbol_Here**> wrote:

Several thing =96 first and foremost The only protection for an oxygen deficient environment is a supplied air source. Thus, a question regarding "respirator fit" raises a flag.

Having supervised the installation of many oxygen sensors in locations where a deficiency can occur, here are some thoughts

The sensor should be located IN the area to monitor and installed according to the manufacturer's instructions. Pay particular attention to the vertical height instruction.

The sensor is low voltage, but the installation still must comply with the NEC.

The alarm should be in the monitored area and repeated just outside the affected zone and also at a central monitoring location.

Provide regular maintenance as required by the manufacturer. While using a two gas calibration to set the span works, some sensors are calibrated with ambient oxygen, set to 20.8%. It is very useful to periodically test the sensor with a low oxygen source.

Most electrochemical oxygen sensors require replacement every two years. In the very dry climate of southern California, we find that they need more frequent replacement..

False alarms from an oxygen sensor should be very infrequent. If false alarms occur with an annoying frequency, work with the manufacturer to fix it =96 false alarms lead to the "chicken little" problem.

Your responders to an alarm, be it maintenance or other, should bring a working 4-gas portable with them to provide a back-up to the installed system.

Finally, installed sensors are really great, but they require active PM and some understanding of their limitations.



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From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of bjwiehe**At_Symbol_Here**OWU.EDU
Sent: Wednesday, August 29, 2012 7:01 AM
Subject: [DCHAS-L] Oxygen Sensor

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


Barbara Wiehe

Ohio Wesleyan University
Environmental Health and Safety / Greenhouse Manager

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