Hi. Not allowed to explode H balloons in class according to my technician and Head of Science unless I have official risk assessment from an official source and it is not in the SoW. Anyone know where or how I can get this? Have done this many times and seen other teachers do it lots in previous schools so a bit perplexed that my current school has never done it and are making such a fuss. Same when I wanted practical for finding fuse ratings of various fuse wires by melting them. Can't do that apparently either. Any thoughts appreciated?