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

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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