LPG Propane cylinders must be located outside of the building in the open air and on a firm base, in a well ventilated area. The must be accessible at all times and unobstructed (not locked behind gates). You will require 1 metre horizontal clearance to any door or air vent or flue terminal and 300mm verticle clearance to any window, or fixed source of ignition. Cylinders must not be located within 2 metres of an untrapped drain. Cylinders should be located against a ridgid structure. If against the building, then this should have a minimum 30 minutes fire resistance. You can fit a non combustible hood over the top of the cylinders, providing it does not obstruct your valves and changeover.