From: Eugene Ngai <eugene_ngai**At_Symbol_Here**COMCAST.NET>
Subject: Re: [DCHAS-L] Hydrogen Fuel Cell Questions-O2 sensor...
Date: Fri, 29 Jul 2016 10:13:03 -0400
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: 003401d1e9a3$52607810$f7216830$**At_Symbol_Here**
In-Reply-To <31F69119-6E61-4E1D-ABC2-C45A3212AD1F**At_Symbol_Here**>

If it is a single cylinder of H2 rather than bulk, O2 sensors will not be beneficial. A typical lab of 20' x 40' x 10' has 8,000 ft3 volume. A H2 cylinder has 250-300 ft3. A worst case leak (release in 1 minute) would barely move the O2 sensor from 20.9%. Most O2 sensors will alarm at 19.5% which OSHA considers to be O2 deficient. The H2 sensor would go off.. In a release like this the explosion hazard is far greater than asphyxiation.


As noted in the e-mails below, O2 sensors can be finicky, many people are not aware that CO2 can poison the sensor. Please see


Eugene Ngai

Chemically Speaking LLC


From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**] On Behalf Of Aaron's Phone
Sent: Friday, July 29, 2016 8:55 AM
Subject: Re: [DCHAS-L] Hydrogen Fuel Cell Questions-O2 sensor...


You are spot on.  The O2 sensors cells are easily poisoned and they need servicing and replacement at regular intervals.   Best of luck and involve your researchers so that they know they are also responsible for their safety and health.


Best regards,

Aaron Chen, MPH, CIH, FAIHA

Sent from Aaron's iPhone.  

On Jul 28, 2016, at 5:35 PM, Margaret Rakas <mrakas**At_Symbol_Here**SMITH.EDU> wrote:

I don't disagree with the suggestions for O2 sensors but it is really important to make sure you get the right oxygen sensor.  We had an awful time with false alarms-which cause a lot of disruption initially as the building clears out and first responders stream in--and then after a bunch of these, people hit mute buttons and/or come up with very novel re-wiring to turn the alarm off.  Talk with someone from the vendor who really understands the different types and what you need for your particular lab set up.  We have several of these for our NMR rooms and since we don't have the same application as you do, I don't feel able to give a more specific recommendation, sorry.



Sent from my iPhone

On Jul 28, 2016, at 3:44 PM, Aaron's Phone <cycling1**At_Symbol_Here**VERIZON.NET> wrote:



I would also use a room O2 sensor for the room.  It helps the team to know if oxygen levels are slipping to dangerous levels because of a H2 leak.  



Aaron Chen, MPH, CIH, FAIHA

Sent from Aaron's iPhone.  

On Jul 28, 2016, at 2:29 PM, Smallbrock, Margaret A. <Margaret.Smallbrock**At_Symbol_Here**SDSMT.EDU> wrote:



I have a researcher who is intending to start work on a hydrogen fuel cell. I want to make sure I have covered all the bases when I talk with him. The hydrogen sensor has already been purchased, but if you can provide any extra guidance, that would be great.


Thank you,


Margaret Smallbrock

Campus Environmental Health and Safety Manager

Environmental Health & Safety

South Dakota School of Mines

501 East St. Joseph Street

Rapid City, SD 57701-3995


605-394-5837 FAX



Previous post   |  Top of Page   |   Next post

The content of this page reflects the personal opinion(s) of the author(s) only, not the American Chemical Society, ILPI, Safety Emporium, or any other party. Use of any information on this page is at the reader's own risk. Unauthorized reproduction of these materials is prohibited. Send questions/comments about the archive to
The maintenance and hosting of the DCHAS-L archive is provided through the generous support of Safety Emporium.