IEC 61730-1 is the first part of the safety qualification standard for photovoltaic modules. It defines the constructional requirements that a module must satisfy in order to be considered safe, and it is applied together with Part 2, which contains the corresponding test procedures. The document begins by establishing the application classes of modules, from the fully accessible class used in unattended systems at low voltage, through the class used in systems with accessible live parts, to the class intended for use in high-voltage installations where the modules are protected from contact, and it shows how the class determines the string voltage that the module may be used at. It then sets out the requirements for the materials and components of the module: the encapsulant, the backsheet, the frame, the junction box and the connectors must all have adequate electrical, thermal and mechanical properties, and the construction must maintain the separation of live parts from accessible surfaces through the whole life of the module. Rules for creepage distance and clearance complete the document.