Buoyancy compensator (aviation)

With a rigid airship two main strategies are pursued to avoid the venting of lifting gas: Only gasses have a density similar or equal to air.

Zeppelins often used a different gas mixture of propylene, methane, butane, acetylene (ethyne), butylene and hydrogen.

In some airships rain gutters were fitted to the hull to collect rainwater to fill the ballast water tanks during flight.

Captain Ernst A. Lehmann described how during World War I Zeppelins could temporarily remain at the sea surface by loading ballast water into tanks in the gondolas.

The silica gel method was tested on the LZ 129 to extract water from the humid air to increase weight.

[citation needed] The most promising procedure for ballast extraction during the journey is condensation of the engines' exhaust gasses, which consist mainly of water vapour and carbon dioxide.

The German-made USS Los Angeles (ZR-3) was also fitted with exhaust gas coolers to prevent jettisoning of the costly helium.

One variation tested on the LZ 127 Graf Zeppelin was to blow heated air on the lifting gas storage cells with the aim to gain buoyancy for launch.