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External influences shall be taken into account when choosing:
*The appropriate measures to ensure the safety of persons (in particular in special locations or electrical installations)
*The characteristics of electrical equipment, such as degree of protection (IP), mechanical withstand (IK), etc.}}

Every electrical installation occupies an environment that presents a variable degree of risk:
*For people
*For the equipment constituting the installation

Consequently, environmental conditions influence the definition and choice of appropriate installation equipment and the choice of protective measures for the safety of persons.

The environmental conditions are referred to collectively as “external influences”.

Many national standards concerned with external influences include a classification scheme which is based on, or which closely resembles, that of international standard IEC 60364-5-51.