IEC 60721的本部分提供了IEC 60721-3所有部分的使用指南。它包含 背景信息，包括课程的应用和限制信息 IEC 60721-3各部分给出了可用于设计的条件限制 以及设备的保护。 为了避免误用IEC 60721-3-0中定义的等级，参考IEC 60721-3-0非常重要 IEC 60721-3的其他部分。购买本文件时可获得的所有当前修订均包含在购买本文件中。

This part of IEC 60721 provides guidance on the use of all parts of IEC 60721-3. It contains background information including information on the application and limitation of the classes given in various parts of IEC 60721-3 which can be used in the design, limitation of conditions and protection of equipment. Reference to IEC 60721-3-0 is important in order to avoid misuse of the classes defined in the other parts of IEC 60721-3.All current amendments available at time of purchase are included with the purchase of this document.