I would re-iterate remarks made earlier after the U of H events. In that case pending release of the full enquiry, the details are yet far from clear. Without implication to the specific events at U of H or elsewhere I offer the following observations:
a) The spark energy required to ignite flammable gas mixtures containing oxygen as opposed to air is very much lower (NFPA 53 suggest perhaps 20 times lower)
b) The explosion pressures developed in pressurized flammable gas/air mixtures are very much higher than mixtures ignited at atmospheric pressure
c) The handling of pure oxygen at pressure and the requirement for and the methodologies of suitable cleaning for oxygen service
d) In the case of preparation of gas mixtures it is clear that the order of preparation would have significant bearing on the degree of enrichment.
e) The selection, installation and maintenance of electrical apparatus in hazardous locations is a specialised task and should only be undertaken by personnel or under the supervision of personnel who are appropriately qualified.
Whilst there is a considerable body of work, largely developed within the electrical community for protection of electrical apparatus in hazardous locations employing techniques such as intrinsic safety, explosion proofing and others in the presence of flammable gas atmospheres - that work has been done based almost entirely on the basis of flammable gases and vapours in mixtures with air at normal atmospheric pressures and temperatures. Pretty much without exception all electrical apparatus on the North American market marked for use in hazardous locations has only been approved for standard atmospheres.
By way of a thought experiment imagine a researcher who choose a temperature measuring device (say RTD or T/C) to measure temperature in an oxygen enriched (but not pressurized) atmosphere containing hydrogen and he assumed that a suitable intrinsically safe zener barrier marked Div 1 Group A, B, C & D according to NEC and installed according to code would be suitably safe. That barrier would be designed to limit the electrical energy to < 19 micro joules considered the minimum ignition energy for hydrogen. NFPA 53 suggests that 1 micro joule might be ignition capable in an oxygen enriched atmosphere with hydrogen. Consider now the static charge of the human body strolling around this laboratory normally assumed in the region of 30 millijoules.
Finally the risks associated with oxygen enriched atmospheres were reasonably understood in the compressed gas industry but came into sharper focus following the disastrous fire on board Apollo 1 https://urldefense.proofpoint.com/v2/url?u=http-3A__www.space.com_14379-2Dapollo1-2Dfire-2Dspace-2Dcapsule-2Dsafety-2Dimprovements.html&d=DQIFAw&c=lb62iw4YL4RFalcE2hQUQealT9-RXrryqt9KZX2qu2s&r=meWM1Buqv4IQ27AlK1OJRjcQl09S1Zta6YXKalY_Io0&m=VSaih5SRptWEiDZevf24gdAPLcc_mNkdmUrRB7CmQGk&s=qsYro7SYfJzHiY8YkNqAryZvrn7dO2DoDIRS_IfcTe0&e= and later publication of NFPA 53.
James Osprey P. Eng. C. Phys
21 090 Daoust, Sainte-Anne-de-Bellevue
QC, H9X 4C7
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**med.cornell.edu] On Behalf Of Reinhardt, Peter
Sent: May-04-16 9:54 AM
Subject: [DCHAS-L] Hydrogen safety webinar?
I would really appreciate it if DivCHAS or AIHA did a webinar on hydrogen safety as it pertains to research laboratories. There have been three hydrogen explosions at universities since 2010 (U. Missouri, Stoney Brook U. and U. Hawai'i). Scientists and EHS staff need better training on hydrogen safety, risks to look out for, and how to do a hazard assessment for research involving hydrogen. When we ask researchers about their setup, they say, "I've been doing this for years. This is the same setup described in the literature/that my mentor uses." Please.
Peter A. Reinhardt
Director, Office of Environmental Health & Safety
135 College St., Suite 100
New Haven, CT 06510-2411
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