I would venture to say it has to do with ISO 10156:2010 which defines the international standard for determining the flammability of gases or gas mixtures.
>5.5 mol% hydrogen in nitrogen is considered flammable
>2.94 mol% hydrogen in argon is considered flammable
It would agree with what you are seeing. I could only guess DOT and EPA are ok with classifying these mixtures using this standard.
Jeff
Sent from Mail for Windows 10
From: Debbie M. Decker
Sent: Tuesday, June 5, 2018 8:35 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
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.
Thanks,
Debbie
Debbie M. Decker, CCHO, ACS Fellow
Past Chair, Division of Chemical Health and Safety
Councilor and Programming Co-Chair
University of California, Davis
(530)754-7964
(530)304-6728
dmdecker**At_Symbol_Here**ucdavis.edu
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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