On Aug 4, 2022, at 11:08 AM, James Kaufman <jkaufman**At_Symbol_Here**LABSAFETYINSTITUTE.ORG> wrote:

With regard to Ralph's second point and 50ml of flammable solvent.  Consider it this way ...

One gallon (about 4,000 ml) of gasoline has enough energy to send a 3,000 lb car with 1,000 lbs of passengers 20-30 miles.  

But the internal combustion engine is only 20% efficient.  If the car could use 100% of the energy, it and the passengers could go 100-150 miles.

But since we only have 50ml (about 1%, if 40 ml), the 4,000 pounds of car and people go about 1-1.5 miles.

Imagine what happens if it detonates and all the energy is released at once (just 50 ml)!  ... Jim

PS.  LSI now has virtual lab inspections, safety program evaluations, document reviews, courses and seminars ... all virtual.  And, a complimentary,  updated version of our classic Laboratory Safety Guidelines is now available on our website ... https://www.labsafety.org/product/lab-safety-rules

4James A. Kaufman, PhD

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On Thu, Aug 4, 2022 at 8:19 AM Ralph Stuart <ralph**At_Symbol_Here**rstuartcih.org> wrote:

> >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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