A chemistry lesson

The chemical composition of propane is C3H8 and butane, C4H10. Because the make-up of each gas contains traces of other gases, there may be small variances in the exact composition. Specification limits are covered by BS 4250.

The terms Commercial Propane and Commercial Butane are often used to describe LPGs of acceptable quality for most applications. For further information, take a look at LPG properties.