From:
James Kaufman <jkaufman**At_Symbol_Here**LABSAFETYINSTITUTE.ORG>
Subject:
Re: [DCHAS-L] Hydrogen Gas Safety
Date:
Feb 25, 2025 16:51 UTC
Reply-To:
ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID:
<CAHk9oERpr_ssYuaoCoC61T_AMNuvQgwx96yaKxHyP1cPDRvOLw**At_Symbol_Here**mail.gmail.com>
In-Reply-To:
<CAPEgXxyv0NkRML-0TrTE4UkamDMHS-Pe9MgdHv6Y7J=4e5+sAQ**At_Symbol_Here**mail.gmail.com>
And here's one more ...
The Joule-Thomson Inversion Temperature for hydrogen gas is minus 75 degrees celsius.
This means that unlike carbon dioxide that gets colder when it comes out of your CO2 fire extinguisher, hydrogen gets hotter. In fact, it can get so hot that it can exceed its autoignition temperature. The result as it mixes with the air can be spontaneous combustion (BTW ... not autoignition).
The resulting explosion killed two at NETL in Pittsburgh in the 50s.
Never let hydrogen gas out of the tank without using a regulator ... Jim
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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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