1. Generally use Class II hand-held power tools, and install a leakage protector whose rated electric shock action current is not greater than 15mA and whose rated action time is less than 0.2 seconds. If using a Type I hand-held power tool, zero protection must also be used. Operators must wear insulating gloves, wear insulating boots or stand on insulating mats. 2. When working in a humid place or under a metal frame, you must choose a Class II hand-held power tool and be equipped with a spill-proof protector. Class I hand-held power tools are prohibited. 3. Class III hand-held power tools with isolation transformers should be used in narrow places (boilers, metal containers, waste water pipes, etc.); if you choose type II portable power tools, you must install a fortification device with an anti-leakage device. Isolation transformers or leakage protectors are installed in narrow places and should be monitored during work.