Hydrocarbons

The hydrocarbon propellants are propane (freezing point —42.1), n-butane (freezing point — 0.5) and isobutane (freezing point — 11.7). Commercial butane is always a mixture of n-butane and isobutane. Mixtures with propane in different ratios are usually used to adjust the pressure. Hydrocarbons are cheap, stable and of low toxicity, but are highly flammable.