Liquefied flammable gas used for space heating shall be supplied from a fuel cylinder located outside of and at least 10 feet from any assembly occupancy. An approved heater and piping system shall be used. Flexible hose in length up to 36 inches may be used if it is designed for a minimum bursting pressure of 1,750 psig, and such hose shall be marked with “L.P.- GAS” or “LPG” labeling.