Electrical Shock Hazard Use only certified nonconductive hoses and fittings. Always wear and use the necessary clothing, equipment and safety practices to protect against electrical shock. Failure toWARNING follow these rules can result in serious personal injury . Make certain the fiberglass extension tube is free from moisture, oil, and grease. The accumulation of any or all of the above-mentioned materials will reduce the insulating properties of the fiberglass extension tube.