In a practical dirigible design , the difference is significant , making a 50 % difference in the fuel-carrying capacity of the dirigible and hence increasing its range significantly . However , hydrogen is extremely flammable and its use as a lifting gas in dirigibles has decreased since the Hindenburg disaster . Helium is safer as a lifting gas because it is inert and does not undergo combustion . The gaseous state of water is lighter than air ( density 0.804 g/L at STP , average molecular mass 18.015 g/mol ) , non-flammable and much cheaper than helium . The concept of using steam for lifting is therefore already 200 years old . The biggest challenge has always been to make a material that can resist it . In 2003 , a university team in Berlin , Germany , has successfully made a 150 °C steam lifted balloon . However , such a design is generally impractical due to high boiling point and condensation
Hindenburg disaster
Hindenburg disaster
Lifting gas