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Previous by Date: Subject: [DCHAS-L] Safety information in the chemical literature Date: Thursday, August 4, 2022 at 8:27:28 AM Author: CHAS membership <membership**At_Symbol_Here**DCHAS.ORG>

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I will add some more.

1. technician was reducing a catalyst in a quartz tube in a hood by flowing less than 100 SCCM of hydrogen oven it at a maximum pressure of 2" WC. The hazard analysis assumed the worst case was a failure of the quartz tube leading to a small fire that "might" damage the furnace. When the quartz cracked, the hydrogen detonated (which I admit surprised the heck out of us) and blew the hoods doors across the room hitting a wall 14 ft away with enough force to mark the paint on the cinder block. The furnace was destroyed and the hood ruined.

2. A heat traced line failed and shorted to the tubing. The hazard analysis assumed the worst case was the tracing would be ruined. Instead it shorted through the tubing and caused a fire that destroyed significant parts of the microunit in the hood.

3. An operator forgot to install a high temperature shutdown TC in a reactor after cleaning. The hazard analysis assumed the worst case of a high temperature was a "leak" which would be "diluted" in the hood. The high pressure reactor seal failed due to high temperature and blew ignitable concentrations outside the hood resulting in a deflagration that wrecked the hood and did substantial damage to the lab.

In all cases no one was hurt. In #1 and 2, the lab was not occupied. In # 3 the operator was well away from the hood and was just scared to death.

And I have many more to share.

My point, like Ralph's excellent comments, are that the hazard analysis of many laboratory operations is too optimistic and colored by a desire to be able to do the work not by an adequate hazard analysis and risk assessment..

Richard Palluzi
BE(ChE), ME(ChE), PE, CSP,FAIChE

Pilot plant and laboratory consulting, safety, design, reviews, and training
www.linkedin.com/in/richardppalluzillc/
www.pilotplants.us

Richard P Palluzi LLC
72 Summit Drive
Basking Ridge, NJ 07920
rpalluzi**At_Symbol_Here**verizon.net
908-285-3782

-----Original Message-----
From: ACS Division of Chemical Health and Safety On Behalf Of Ralph Stuart
Sent: Thursday, August 4, 2022 8:18 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: Re: [DCHAS-L] iron pentacarbonyl

> >Explosion proof has two meanings when applied to a hood.
>
I have had two specific experiences that were impacted by this confusion:

1. I had a call from a lab tech who was concerned because they had an explosion in a standard fume hood and the projectiles had cracked the sash. Replacing the sash would going to cost most than $1000. They wanted an assurance that the replacement wouldn‰??t crack if the same explosion happened again. My response was ‰??How big an explosion are you planning on having in the fume hood?‰??. There was no response when they realized that an explosion was not part of their work plan‰?|

2. We had an explosion in a household style refrigerator on another campus. This laboratory had left isopentane in the refrigerator over night to cool down for use the next day. The isopentane leaked into the cooling compartment and when the thermostat flipped on, the resulting spark triggered the explosion. We learned in discussions with the lab tech, the amount of isopentane likely to have leaked was less than 50 ml. But the amount of energy when the solvent ignited in a sealed container was enough to destroy the refrigerator, scatter lab debris across the lab, and pop out all the ceiling tiles in the room. Fortunately, there was no one in the room when the explosion occurred. The point is that there is a lot more energy in small amounts of solvents than people using these chemicals as reagents recognize.

- Ralph

Ralph Stuart, CIH, CCHO
ralph**At_Symbol_Here**rstuartcih.org

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