Based on the video and the fact that it was under construction, it was likely to be an acetylene cylinder explosion. Sometimes welders accidentally torch the side of the cylinder causing a decomposition reaction to be initiated. If the cylinder interior matrix has been damaged, the reaction can be self sustaining and the cylinder can rupture up to 24 hrs later. Unlike the US there are no pressure relief devices on acetylene cylinders in Europe. In my opinion, the explosion in the video is definitely a acetylene cylinder rupture followed by a fireball. The Europeans have special HazMat rules on acetylene cylinders for this reason. In the UK after a acetylene cylinder has been exposed to a fire they will evacuate for a distance of 100 meters for 24 hours. I train HazMat responders to do a full thermal inspection of the cylinders. We used to train rookie firefighters to feel the side of the cylinders for hot spots.
Damaged acetylene cylinders can be very unstable. I participated in a decommissioning of 2 in the middle of Brooklyn in 2017. FDNY did not feel safe to transport the cylinders out of the city. WE disposed of them in the middle of a busy street with blast barriers surrounding the cylinders
Eugene Ngai
Chemically Speaking LLC
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Anna Sitek
Sent: Thursday, January 17, 2019 5:50 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] FYI - Fire ball on University roof in France
Anyone have further details on this impressive video?
Three people have been injured in a massive explosion at a university building in Lyon, France.
Footage of the blast shows a fireball erupting into the sky above the building where a large fire could already be seen on the roof.
The building on the La Doua campus in Villeurbanne, north of Lyon city centre, is a science library.
The area has been evacuated and firefighters are on the scene.
Police told Reuters works were being carried out on the roof and the fire began after a gas bottle exploded.
The university told AP construction work was the cause and the explosion was "accidental".
The university said multiple explosions occurred and had been "caused by renovation work."
Images posted on social networks showed massive plumes of black smoke and flickering flames rising above the campus in the Lyon suburb of Villeurbanne.
Many captured the moment of the largest blast which sent a mushroom cloud metres into the air above the science building.
Authorities in the city and university insisted there were no risks of chemical leaks.
--
Anna Sitek, CSP, CCHO
Research Safety Professional- College of Science & Engineering
Department of Environmental Health and Safety
University of Minnesota- TCEM
Lab Safety Resources www.z.umn.edu/labsafe
Joint Safety Team www.jst.umn.edu
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