Hydrogen burns with an invisible flame. Most of the flame you see on exploding airships is due to the burning of the materials its made of. I do remember the demo for that. You need to regulate the mix of hydrogen or you end up with a big bang, but I guess that applies to most stuff. Ammonia is extremely dangerous if you breathe in its fumes. Its used as a coolant on the ISS for the outside radiators, and if they are ever servicing those as they do get issues, they have to be very careful not to bring frozen ammonia into the main cabin as it can poison filters and is a dangerous substance to humans. Its interesting, as we used to use a lot of it in technical drawing copy equipment as a developer. The place stank, even with all the extractors and regulation gear installed.
I'm assuming its the vapour then, not the actual liquid that you can burn? Brian