This document is applicable to respiratory protective devices except diving apparatus. NOTE Definitions for diving apparatus are given in EN 250. This document defines commonly used terms and definitions and specifies units of measurement to achieve a uniform interpretation and to prevent ambiguous use. It indicates graphical symbols that may be required to be placed on respiratory protective devices (RPD) or parts of RPD or instruction manuals in order to instruct the person(s) using the RPD as to its operation.