Talking of school science demonstrations, I was doing a long supply stint in Eggbuckland (plimurff) and had to cover the topic of respiration/breathing/gass transfer thing. It's pretty bloody dry and boring and I thought it would be a fine thing to drag my Davy lamp in (which I used for it's purpose in mines) and demonstrate how these things actually work....
There's a misconception that it's a lamp for lighting in coal mines....which doesn't cause the methane to "go off" rather than it being an instrument to inform of atmospheric characteristics and changes.
I bought my gas monitor in, and had a big bell jar to whack it all in. I thought "this is quite a boring lesson where everyone easily gets the outcome, at least they can learn exactly how a davy lamp works!!!"
As demonstrations go, it's quite boring....watching a weeny flame change in the slightest way. The gas cap on the methane flame is pretty good as well and then the silent pop when LEL is reached.
At that point, the labtech woman, who was a flowery, middle aged, menopausal old hitler came in and went utterly off the scale at me for "using a piece of apparatus which had not been signed off by CLEAPPS" (who are the remote box ticking authority for science lessons, as graduate scientists haven't got a clue about relevant hazards). I couldn't reason with her tiny mind and there endedeth the lesson!
Bloody nanny state gone maaaad.