Electric power operated tools must be of what type?

Electric power-operated tools must be of the approved, double-insulated type to ensure the highest level of safety for users. Double insulation is a safety feature that provides an additional layer of insulation, reducing the risk of electric shock. This design means that even in the event of a failure in the primary insulation, the tool remains safe to use because the inner insulation protects the user from any electrical parts that could be exposed.

Tools that are double-insulated do not require a three-wire electrical system, as they can operate safely without a ground connection. This is particularly important in environments where tools might come into contact with water or other conductive materials, making the additional insulation critical for user safety.

The other options provided do not meet this essential safety standard. Tools classified as standard or single-insulated may lack the necessary protective measures and could pose a risk of electrical shock. Hence, the requirement for approved, double-insulated tools is a crucial aspect of electrical safety practices, especially for plumbing applications where water is frequently present.