Why is hydrogen no longer used in air balloons?

For small balloons like individuals often have for recreational use, hot air is much easier to control than either hydrogen or helium.

For the occasional blimp, or long distance balloon trip, Helium, while somewhat heavier than Hydrogen, has proven to be far safer.

The Hindenburg has proven the inherent dangers of using Hydrogen Gas in blimps. While, in theory, pure hydrogen is not explosive without the presence of oxygen, any rupture in the thin material separating hydrogen from the air atmosphere can prove to be deadly.