When you buy a gas cylinder for the first time, you must pay for both gas and the cylinder. If you want to exchange an empty cylinder for a full one, you only need to pay for the gas unless you have a 21 kg “old red” balloon (these cylinders are no longer filled or sold.)
Pure propane or technical propane is a hydrocarbonic liquefied gas used for different production and technological purposes. In production liquefied gas comprises a wide spectrum of heat treatment of various parts and surfaces. For example, burning of pure propane is used for metal cutting or drying of painted surfaces.