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DCHAS-L Discussion List Archive

From: Daniel Crowl <crowl**At_Symbol_Here**MTU.EDU>
Subject: Re: [DCHAS-L] 4% vs. 5% hydrogen
Date: Tue, 5 Jun 2018 19:28:56 -0600
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: CAPEgXxy+BTMv1wu_DEfOcW_dOyx_-05matX5ZoHfN1KbM7XrrQ**At_Symbol_Here**mail.gmail.com
In-Reply-To


Hi Debbie,

I think the flammability issue is based on whether the mixture will become flammable if it leaks out and mixes with air. The 5% hydrogen with nitrogen will likely go thru the flammability zone on a triangle diagram as it mixes with air - that will create a flammable mixture. I could use this as a homework problem for my chemical engineering students.

With the argon mixture, it probably does not intersect the flammability zone since the hydrogen is at a slightly lower concentration. In this region of the flammability zone the results are very sensitive to concentrations.

This is a lot more complicated that just upper and lower flammability limits. You need to draw a triangle diagram with one axis nitrogen, one axis hydrogen and one axis oxygen, There is a flammability zone on this diagram. To draw an approximate diagram and flammability zone you need the upper and lower limits and the limiting oxygen concentration.

I also suspect that a 4% hydrogen in nitrogen mixture would also not be flammable when mixing with air.

Dan Crowl

On Tue, Jun 5, 2018 at 6:35 PM Debbie M. Decker <dmdecker**At_Symbol_Here**ucdavis.edu> wrote:

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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