Volatiles
From Unofficial Stationeers Wiki
Volatiles are gases that can be used as a fuel. It requires the presence of Oxygen for combustion.
Different ratios of Volatiles and Oxygen will produce different temperatures and pressures during combustion. Combustion will create a large amount of Heat, pressure, and Carbon Dioxide. This reaction is useful inside a Furnace for smelting ores and creating alloys, but can be catastrophic when inside a Canister or a Room.
Currently, it is labeled in the atmospheric analyzer as H2. However, during Combustion will behaves more like methane (CH4) creating a large amount of Carbon Dioxide and heat instead of Water typical of a Hydrogen + Oxygen reaction.