Lab Fires 4/3/23

Thoughts with Richard Bleil

There is a problem with lab fires.  The story comes down of an academic laboratory fire when the firefighters decided to sweep the entire lab with a water spray.  Unfortunately, in the fume hood there was a large beaker filled with sodium metal.  As soon as the water hit the beaker, the water got through the solvent covering the sodium to keep it from reacting with moisture in the atmosphere, and the entire beaker exploded. 

Sodium is famous for exploding in water.  It’s actually not the only chemical that will do so, and it certainly isn’t the worst.  For example, potassium explodes with far more violence and far more rapidly.  What really happens with either of these metals is that the metal (sodium or potassium) breaks down the water to form a hydroxide (potassium hydroxide or sodium hydroxide, both very corrosive alkaline compounds).  This electrochemical reaction is so violent that it creates sparks as it does so.  The side product of the reaction is hydrogen gas.  As soon as the hydrogen concentration reaches a sufficiently high concentration, the spark from the reaction will ignite the hydrogen causing it to react with oxygen in the air, creating the well-known explosion and resulting in, ironically enough, water vapor.

Firefighters often don’t think about the fact that some metals react violently with water.  They do have experts that understand chemical reactions, but your typical firefighter has never really studied science, let alone chemistry.  As a result, they need an expert on hand.  Today, they ask the chemist in charge of the lab that is on fire accompany the firefighters so they have an idea of what to expect. 

It’s interesting that the default for these firefighters wasn’t a chemical foam or something that wouldn’t react with chemicals, not to mention the plethora of electrical plugs found in any laboratory, but there it is.  I’ve written before about my own adventure in a potential bomb risk, which fortunately turned out to be nothing.  And of course, I did find a shock sensitive explosive in my first lab, so I guess I’ve had my share of adventures.  I’ve never had any training in handling danger, but as a chemist (and a single one at that), I’m still expected to know how to respond, and I would like to think that I do.

Handling toxic chemicals is part of life for a chemist.  I have a good friend who sold me cancer insurance when I was teaching.  One of the questions for the form was if I smoke or not, which I do not, but they never asked me if I play with carcinogenic compounds.  There is a chemical that is so deadly that if you take one drop of it and put it in a full sized swimming pool, and take one drop of water from that pool and put it in a second pool, the concentration in the second pool is still high enough to kill. 

This is why, when I taught, I always took so much care to go through safety procedures.  I do know that it paid off once when a student told me about what happened in the dorm.  Doing her laundry, one of the driers caught on fire.  Because of the training she had in my class, she tells me that she knew how to properly operate a fire extinguisher, something that everybody should know, but few actually do. 

In my house, I have a fire extinguisher near each door.  The placement is strategic, because the most extinguishing medium in any fire extinguisher is only about thirty seconds.  They’re not designed to be used if the entire house is on fire.  In the movies where somebody rushes into a burning building armed with only a fire extinguisher would, in the real world, never rush out again.  With the position of the fire extinguishers in my house, if I need to use it I know that there is a safe pathway behind me just in case it fails. 

To use a fire extinguisher, you want to point the stream at the base of the fire, not the middle.  If you point at the middle of the flame, there’s a good chance the fire retardant will brush the flames towards you.  Sweep back and forth and be ready for the noise because fire extinguishers are quite loud.  Brace your nerves and use the entire contents until the extinguisher is empty.  Do not stop to “check” to see if the fire is out because if it isn’t, the flames will reignite and you’ve likely used half of your media or more. 

Sometimes it’s necessary to put yourself in harm’s way, but remember that you’re important as well. 


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