Sch 1 para 7 Selection of materials
(1) The materials used for the construction of equipment and protective systems must not trigger off an explosion, taking into account foreseeable operational stresses. (2) Within the limits of the operating conditions laid down by the manufacturer, it must not be possible for a reaction to take place between the materials used and the constituents of the potentially explosive atmosphere which could impair explosion protection. (3) Materials must be so selected that predictable changes in their characteristics and their compatibility in combination with other materials will not lead to a reduction in the protection afforded; in particular, due account must be taken of the material’s corrosion and wear resistance, electrical conductivity, mechanical strength, ageing resistance and the effects of temperature variations.