Alert regarding hydrogen balloon explosions: We recently had an accident with a hydrogen balloon catching fire and melting, rather than popping. Has anyone else had this and how do you prevent it happening again.

Previously, I have never had a problem, but this is the second incident this year. This time, the molten balloon has gone onto the teacher’s hand, causing a nasty burn and previously, the molten balloon dropped causing a minor burn to a desk and the floor.

I have now banned the practical activity here until the solution to the problem is found. I am currently using Helium quality balloons, as I couldn’t buy my usual cheap thinner ones and am wondering if this is the issue. Any ideas would be appreciated.