Hydrogen is highly inflammable, that means it easily reacts with oxygen and when it burns water is produced. Exactly this characteristic makes it suitable as a fuel.
Hydrogen has no greater danger potential than oil, natural gas or uranium. With regard to its physical and chemical properties hydrogen is not particularly dangerous. Therefore, e.g. in Germany, the safety precautions and regulations for hydrogen do not differ from those for every other burnable gas.
In car accidents or air crashes liquid fuels often lead to fire slicks and in consequence frequently result in fatal injuries. It is characteristic for hydrogen to escape upwards into the air very fast. On the other hand there is an increased explosion hazard when hydrogen is set free in closed rooms, e.g. in garages or tunnels. In closed rooms good ventilation and perhaps additional safety precautions have to be provided for.
The chemical industry has been using hydrogen for hundreds of years. The experiences concerning the safety are regarded as good.
The burst of fire which destroyed the zeppelin LZ 129 "Hindenburg" in Lakehurst was not caused by the hydrogen on board as a means for lifting. The cause of the disaster were the chemical and electric features of the coat of paint of the "skin" of the airship together with the special weather conditions on the day of the disaster in Lakehurst. In an atmosphere of thunderstorms, the extremely combustible exterior painting was inflamed by an electrostatic discharge. After that the fire spread to the hydrogen.
If the airship had exploded as often stated, this photograph could not have been taken. In fact the hydrogen burnt off towards the top. All the passengers who did not leap off survived! If a fluid fuel had caught fire, the catastrophe had been much more disastrous, as fluid fuel always runs downwards and forms a fire slick!