Not sure where you're coming to this from so forgive me if I overexplain. I'm looking at this largely from a transportation perspective which is where most of the interest in hydrogen arises.
To add a not insignificant tidbit: hydrogen is flammable in air at practically all concentrations unlike gasoline, propane, butane, etc.
Also: The minimum ignition energy of hydrogen in air is one of the lowest among known substances at 0.02 mJ, and hydrogen-air mixtures can ignite with 1/10 the effort of igniting gasoline-air mixtures
Or, a good way to describe hydrogen, something that CPFers can understand... it's the lithium of the gas world, something readily apparent given they are both column 1 on the periodic table.