I don't know the proper air fuel ratio for hydrogen but I know it makes a loud bang. It was 1958 or 59 which ever year I took high school chemistry, that a friend and I decided to make a hydrogen generator the way we had just learned in school. There was a local Union Carbide facility in our residential neighborhood that took up most of the block. It was fenced with a small second fenced enclosure near the gate. We knew they kept acid locked in it. We waited till a man brought out a small plastic drum to put into the cage and asked him for a quart so we could get extra credit in a chemistry class project. He gave us a small amount and told us it was depleted acid. We went to a restaurant for oyster shells and set up our generator in the attic of my friends 's garage. The "depleted" acid tested positive for both nitric and hydrochloric acid. The generator worked fine blowing up balloons until we saw they were blowing up larger and larger and keeping us busy, and the vessel was getting too hot to touch. We shut it down with baking soda and emptied it out side. His dad never understood why grass would n't grow in that spot. The balloons were fitted with fuses silmilar to cherry bomb fuse which was available then. We Stood on the balcony of the attic, lit the fuse and let the balloon go. At about 60 feet up the explosion brought people outside and shook leaves out of the trees. After about four balloons, we saved the others till after dark. We never figured what Union Carbide used that created the "depleted" acid.