From: Whitney Rochelle Hess <wrhess**At_Symbol_Here**MIT.EDU>
Subject: Re: [DCHAS-L] 4% vs. 5% hydrogen
Date: Wed, 6 Jun 2018 01:38:27 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: 1E916DD1F7B7064CA3FCF8DF6F9BA213015F7000A9**At_Symbol_Here**

Hi Debbie,

This is related to the molar heat capacity of the inert gas. The larger the molar heat capacity, the greater the inerting effect. Argon has a smaller molar heat capacity compared to nitrogen, so a lower concentration of H2 in argon would support flame propagation. ISO 10156 is a good reference for this.

Whitney Hess, PhD
EHS Coordinator
Microsystems Technology Laboratories
MIT, Room 39-213
Phone: 617-253-8567
Email: wrhess**At_Symbol_Here**

From: ACS Division of Chemical Health and Safety [DCHAS-L**At_Symbol_Here**PRINCETON.EDU] on behalf of Debbie M. Decker [dmdecker**At_Symbol_Here**UCDAVIS.EDU]
Sent: Tuesday, June 05, 2018 7:34 PM
Subject: [DCHAS-L] 4% vs. 5% hydrogen

Hi all:


Riddle me this - why is 5% hydrogen in nitrogen considered NOT flammable and 4% in argon considered flammable?  Tried to reach Praxair but no one is home.


This makes absolutely no sense to me.





Debbie M. Decker, CCHO, ACS Fellow

Past Chair, Division of Chemical Health and Safety

Councilor and Programming Co-Chair

University of California, Davis





Birkett's hypothesis: "Any chemical reaction

that proceeds smoothly under normal conditions,

can proceed violently in the presence of an idiot."



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