There’s been a lot of safety on the blog this week. One recent accident I haven’t talked about is an azide explosion at Minnesota – C&E News, though, has plenty of coverage. Back in June, a grad student was injured when a batch of trimethylsilyl azide exploded – a 200 gram batch. As more details came out, it turned out that the student had reached in to adjust a thermometer on the reaction setup, and was wearing no protective gear:
More important than the reaction, Tolman emphasizes, is the deeper root cause of the incident: insufficient recognition of the reaction’s hazards. Warnings included with literature protocols were “pretty lame,” he says. He also thinks that the lab group became became complacent after doing the reaction several times without incident. “While they were aware of the hazards, concern about them became less up front,” he says.
Indeed. This just emphasizes the sort of thinking I was talking about the other day, the “What’s the worst that could happen?” exercise. In the case of two hundred grams of azide, the worst that could happen should be apparent to anyone who’s being let loose in a graduate chemistry lab: that thing could blow up. I notice that the student involved is quoted as saying that he’s learned that the hazards involved in running a reaction (even an Org. Syn. prep, which this was based on) are not necessarily made clear in the literature. While that’s true, the hazards of 200g of sodium azide going to the TMS azide should have been clear from the start. This, to me, was not a failure-to-warn; this was a failure-to-realize, as the department chair says in that quote above.
There was a lot of good discussion at Chemjobber’s blog when this happened (here as well), with one commenter noting that 200g of trimethylsilyl azide costs about $600. That, to me, illustrates another problem: it’s well worth six hundred bucks to keep someone from having to do an azide reaction of that size in your lab. I know that funding is tight and that academic labs can’t just trot out and buy all the reagents they need, but still.
More recently, a letter to C&E News mentions that no one at the university has been talking about blast shields. The response is that these things are sort of the last line of defense, and that a higher-level review (“Should we be doing this at all?”) would be a more general solution. That’s true, but people are going to set up reactions of all sorts, at all hours, especially in an academic lab. You can’t keep an eye on everyone, all the time, not even close. But even if the plan of a large-scale azide prep gets carried out, a general recognition that you shouldn’t be near the thing without barriers and PPE would be pretty useful. Now, it’s true that on that scale many blast shields are only going to be able to do so much, but they can at least soak up some shrapnel, and I’m just baffled by anyone setting up a reaction even remotely like this without having one in place.
It all gets back to thinking about what you’re doing, and there’s no form to fill and no box to check to make a person do that. Always think about what the most likely problem might be with a reaction, and what the worst problem might be. If you’re heating up two hundred grams of sodium azide and that answer to both questions isn’t “This could blow up and kill me”, then there are even bigger problems that need to be addressed.