The propane powered forklift is one of a class of internal combustion (IC) powered forklifts. The others are run by either gasoline, diesel, or compressed natural gas (CNG). The former has one distinct advantage over its equally powerful brethren. Provided there's sufficient indoor ventilation for its low emissions, the propane powered forklift can be used indoors as well as outdoors.
Due to heavier emissions, the other IC forklifts can't be used indoors at all. Propane forklifts also don't require the purchase and installation of large storage tanks and pumps for gasoline or diesel.
All you need is space enough for a few forklift propane tanks to keep on hand, and these can be supplied by an LP vendor. Propane is also cost effective compared to other IC fuels and is considered healthier for operators.