scope:

It is required that when graphic symbols are used from this standard or another standard, that have a similar or identical shape or configuration, and are shown on the same drawing or set of drawings, steps shall be taken (such as: reference or caution notes, comparison charts, illustrating the conflicting graphic symbols together with proper identification, etc.) to avoid misinterpretation of the symbols used. This requirement is especially critical if the graphic symbols used are from different disciplines and, therefore, represent devices, conductors, or lines of flow, that if misinterpreted might cause damage to the equipment or be dangerous to the life of servicing or operating personnel.