From: Richard Palluzi <000006c59248530b-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
Subject: Re: [DCHAS-L] Hydrogen gas exhaust
Date: Mon, 6 Dec 2021 11:07:17 -0500
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: 00af01d7eabb$579845a0$06c8d0e0$**At_Symbol_Here**

The codes require at least 1 CFM of exhaust (which is not exactly SCFM but close enough) per SF of floor area of the entire enclosed room. So if you have your room area you have your CFM.


Please remember this is the MINIMUM the code allows. It actually puts the burden on the user to determine if an explosion hazard exists (which it often does even at 1 CFM/SF) and if area electrical classification is required.


Please see the following references or feel free to call my cell.


Area Electrical Classification in Research Applications: Is It the Only Mitigative Choice? (Chemical Engineering, Feb, 2021)

Install Ventilation to Reduce Area Electrical Classifications, (Chemical Engineering Progress, August, 2020)


Ventilation Dilution: A Safe Way to Avoid A Fire or Explosion or a Placebo?,

Laboratory Area Electrical Classification,

Ventilated Enclosures for Lowering Area Electrical Classification,

Ventilated Enclosures: Why Do They Often Fail to Work Properly,







Richard Palluzi



Pilot plant and laboratory consulting, safety, design, reviews, and training


Richard P Palluzi LLC

72 Summit Drive

Basking Ridge, NJ 07920




From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Margaret Rakas
Sent: Monday, December 6, 2021 10:42 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] Hydrogen gas exhaust


Good (?) morning,


I am trying to determine the minimum exhaust for hydrogen gas (not liquified) and see that in NFPA 55, section requires a minimum exhaust of 1 scf/min/ft2.  I had to look up scf--it is 'standard cubic foot' and is defined as 1 cubic foot of natural gas at 60F and normal atmospheric pressure.


If I know the size of the room and air changes per hour, is it possible to calculate my exhaust without doing an experiment?


MANY thanks!



Margaret A. Rakas, Ph.D.
Lab Safety & Compliance Director
Clark Science Center
413-585-3877 (p)

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