Combustible substances , with the exception of flammable liquids,may be stored in storage areas in which there are no more than 50 full compressed-gas cylinders-of which a maximum of 25 of them contain flammable, oxidizing or toxic gases-provided the storage area for compressed-gas cylinders is separated by an at least two-metre high wall made of non-combustible building materials. Alternatively ,there must be at least five-metres distance between the gas cylinders and the combustible substances.