> >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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