This part of IEC 60664 applies to assemblies protected against pollution by the use of coating, potting or moulding, thus allowing a reduction of clearance and creepage distances as described in part 1 or part 5. This standard also applies to all kinds of protected printed boards, including the surface of inner layers of multi-layer boards, substates and similarly protected assemblies. In the case of multi-layer printed boards, the distances through an inner layer are covered by the requirements for solid insulation in part 1. This standard refers only to permanent protection. It does not cover assemblies that are subjected to mechanical adjustment or repair. The principlies of this standard are applicable to functional, basic, supplementary and reinforced insulation.