From:
Daniel Crowl <crowl**At_Symbol_Here**MTU.EDU>
Subject:
Re: [DCHAS-L] Hydrogen Gas Safety
Date:
Feb 24, 2025 23:03 UTC
Reply-To:
ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID:
<CAPEgXxyv0NkRML-0TrTE4UkamDMHS-Pe9MgdHv6Y7J=4e5+sAQ**At_Symbol_Here**mail.gmail.com>
In-Reply-To:
<CAAszpkwm=Y=FH4mevV4WpoKw5xEqD=RXUCMvALW6qOiW1TGAzw**At_Symbol_Here**mail.gmail.com>
HI All,
There are several major problems with hydrogen:
First, the flammability limits for hydrogen are wide, with a lower limit of 4.0 vol. % and upper limit of 75.0 vol. % This compares with methane with an LFL of 5 V% and a UFL of 15.0 V%.
Also, the minimum ignition energy for hydrogen is 0.018 mJ compared to 0.280 mJ for methane. A mJ is the energy to drop a penny a few mm.
Also, when it burns, it has a colorless flame (no carbon). So the combustion might not be visible.
Hydrogen is not odorized like natural gas, so a leak is difficult to see or smell.
When I did research using hydrogen, everything - including the gas cylinder, the entire experimental apparatus, and all plumbing and valves, was in a walk-in hood with the air flowing all the time.
Dan Crowl
Good morning-
We have 3 different cylinders of hydrogen in use in one lab (different grades for different pieces of equipment ) and have the following questions (I've searched the web but am not sure what is done with relatively small amounts of hydrogen versus a lab that has higher number in use or a 'tank farm' setup.
1) Do you routinely use excess flow shutoff valves? We do have flame arrestors in line with each regulator....
2) How long are regulators (for inert gases as well as hydrogen) used before refurbishing or replacement? Apparently hydrogen gas can embrittle metals...
3) If you send them out for refurbishment I would be interested in knowing where, and how you know their initial age?
thanks very much!
Margaret
-- Margaret A. Rakas, Ph.D.
Lab Safety & Compliance Director
Clark Science Center
Smith College
413-585-3877 (p)
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