Helium vs Hydrogen Balloon
Hydrogen was historically used in hot air balloons because of its low density, which provided buoyancy to lift the balloon ⬆️ But hydrogen is highly flammable and can lead to catastrophic accidents if ignited.
There was the infamous Hindenburg disaster in 1937, where a hydrogen-filled airship caught 🔥 Ever since the Hindenburg disaster and advancements in materials technology, helium became the much preferred gas for hot air balloons and airships. Helium is non-flammable, making it a safer alternative to hydrogen.