160 Tool Safety: Basic

Double-Insulated Tools

Approved double-insulated tools are constructed with two separate insulation systems or an equivalent reinforced-insulation system. They do not require equipment grounding. Although this design reduces the risk associated with grounding deficiencies, an electric-shock hazard can still exist.

Double-insulated tools are often used in areas where there is considerable moisture or wetness. Although the user is insulated from the electrical wiring components, water can still enter the tool's housing. Ordinary water is a conductor of electricity. If water contacts the energized parts inside the housing, it provides a path to the outside, bypassing the double insulation. When a person holding a hand tool under these conditions contacts another conductive surface, an electric shock occurs.

If a power tool, even when double-insulated, is dropped into water, the employee should resist the initial human response to grab for the equipment without first disconnecting the power source.

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