I worked as a project engineer in a hydrogen fuel cell test lab for a few years. H2 is EXTREMELY hazardous. It can be ignited by a miniscule amount of energy (i.e. a tiny static spark will do it), and it has a very fast flame front, which creates an extremely energetic explosion. It's also the smallest molecule, so it's very difficult to prevent leakage, and it embrittles and degrades most steels over time. Additionally, proton exchange membrane fuel cells (the most common kind) are poisoned by anything NOT H2, so you can't add odorous agents to H2 to easily detect leaks, like we do with natural gas. H2's only non-dangerous characteristic is its high buoyancy, which means it dissipates quickly in outdoor environments, but in my opinion that is not sufficient to offset all of its other dangerous characteristics.
I would NEVER live in a building that had H2 stored inside (as in, inside a vehicle tank) or pumped in it, and I would definitely not trust the general public to use it safely.
It also has to be stored at either incredibly high pressures (as a gas) or incredibly cold temperatures (as a liquid), neither of which are conducive to large-scale, long-range transport.
But the worst part of H2 isn't how dangerous it is or how impractical it is; the worst part of H2 is how incredibly inefficient a hydrogen economy would be. See Paul Martin's excellent summary of H2 for a thorough debunking of the main H2 talking points.
https://www.linkedin.com/pulse/distilled-thoughts-hydrogen-p...