Why is helium preffered to hydrogen in inflating dirigibles?

Helium is preferred to hydrogen for inflating dirigibles primarily due to safety concerns. Helium is non-flammable and inert, making it a much safer option compared to hydrogen, which is highly flammable and poses a risk of explosion. Additionally, helium is more abundant and stable under varying atmospheric conditions, contributing to the overall reliability of airships. This combination of safety and stability makes helium the material of choice for modern dirigibles.