laotou, I would stop that practice here just in case. Most vendors probably do not use hydrogen, but a lungful of hydrogen would be *no laughing matter* (sorry, I couldn't resist).

Just light the baloon, it wont explode like a hollywood scene but it will make a fireball and a whoosh..

Did you know hydrogen gas is produced in dangerous quantity when charging a lead acid battery?
A dozen or so Electric scooters charging at the same time in an enclosed area is very dangerous....how many housing complexes have this scenario?