Propane is under pressure so that it becomes a liquid and is stored in a pressurized tank. Methane is a major component of coal gas. Methane, like propane, consists of carbon and hydrogen. A molecule of methane has only one carbon atom while a propane molecule has three carbon atoms. You can probably guess that octane has eight carbon atoms per molecule.
Some fire extinguishers contain bicarbonate of soda, treated to prevent caking.
Some others produce foam while others produce carbon dioxide. Before the widespread use of electric lights, gaslights were used. They consisted of an open flame that needed to be ignited nightly. It is a nuclear reaction where two molecules are combined to form one with a huge release of energy as heat, light, and probably sound. The dog of choice by fire departments is the Dalmatian.