Liftgas

Liftgas is a processed form of "sturbane", a naturally occurring gas in Oceanyka. The latter is found in shallow deposits, usually near uranium which might or might not be a radiological hazard to the entire airship industry. Regardless, through unknown means liftgas is extremely effective at what its name suggests, once heated up. It is also extremely efficient at high altitudes and has little leak through most fabrics and metals. It is coloured green, odourless, tastes like copper and can cause strokes in very high concentrations.