Portable electric tools and equipment such as cords, plugs, and GFCIs should be inspected before use by both the issuer and the user for signs of chaffing, cracking, wear, or other forms of faulty insulation; evidence of a faulty grounding conductor, cracked plug, or receptacle housing; bent or missing plug or connector prongs; dead front plugs, receptacle, or connectors; a missing, bent, or otherwise abused switch; or an improperly functioning trigger lock (dead-man's switch). While in use, tools and equipment should be observed for proper operation, including any signs of overheating or excessive sparking. Portable electric tools, equipment, and GFCIs should be inspected or trip tested by the user each day before use. Signs of a defect shall require the return of the device for repair.

8.3.2 CONDITIONS OF USE

Portable electric tools, equipment, and GFCIs shall not be used in hazardous locations unless marked to indicate suitability for such use.

Portable electric tools and equipment shall not be handled or suspended by their cords. Tools and equipment shall be used only for their intended purpose, and when guards are required, such guards shall be in place and functional.

Tools and equipment shall be grounded via the case, double-insulated, specially approved low voltage types, or self-contained, battery-operated. (See NEC Section 250-45).

Tools and equipment used in damp areas should be approved for such use. Generally, electrical tools are not approved for use in wet or damp areas without other means of protection.

8.3.3 USE OF EXTENSION CORDS

Use of extension cords should be minimized. Such cords shall be suitable for the intended use, such as waterproof connectors for wet or damp areas, and are subject to the same conditions as the tool or equipment cord.

For the conditions of use pertaining to flexible cords, refer to NEC Sections 240-4,400-7,400-8, Ex. 3, and 29 CFR 1926.405(g).

Extension cords should be visually inspected before each use.

Extension cord sets used on construction sites and used with portable metal electric tools and appliances shall be of three-wire type and shall be designed for hard or extra-hard usage. Flexible cords used with temporary and portable lights shall be designed for hard or extra-hard use. OSHA recognizes hard-service cord (types S, ST, SO, and STO) and junior-hard service cord (types SJ, SJO, SJT, and SJTO) as suitable for extra-hard and hard use.

Note: Extension cords approved for outdoor use may be identified by "outdoor" or "W-A" on the jacket.

Flexible cord sets shall be listed as an assembly by a national recognized testing laboratory (See Section 2.5). Flexible cord sets used on construction sites shall contain the number of conductors required for the circuit plus an equipment grounding conductor. The cords shall be hard use or extrahard use as specified in the NEC.

8.3.4 DOUBLE INSULATED TOOLS

The NEC references the use of Double Insulated Tools in NEC Sections 250-42(f) Ex. 4, 250-45(b) Ex. 3, 250-45(c) Ex., 250-45(d) Ex. 2,422-8(d)(2), 625-9(a), 625-9(b) Ex., 625-9(d) Ex., 680-22(a) Ex. 4, 680-28, and 680-30. UL Standard UL 1097 "Double Insulation Systems for Use in Electrical Equipment" provides the requirements for equipment marked "Double Insulation" or "Double Insulated". Since the end product standard take precedence, the end-product UL Standard should also be consulted when there are questions pertaining to products that require double insulation.

Double insulation is a system comprised of two insulation systems (basic and supplementary) that are physically separted and are not subjected to temperature, contaminants and other deteriorating factors at the same time.

Basic insultion is applied to live parts to provide protection against electrical shock. Supplementary insulation is independent of the basic insulation and provides protection against electrical shock in case of failure of the basic insulation. Also of importance is the reinforced insulation which consists of one or more layers of insulating material that, in itself, provides the same degree of protection as double insulation.

For example, two layers of insulation separating an armature lamination from an armature conductor is not double insulation. This is reinforced insulation. To achieve a double insulated system, one layer of insulation separates the armature lamination from the armature conductor (basic insulation) and an insulating sleeve provides a second layer between the armature lamination and the motor shaft (supplementary insulation).

Generally, double insulated equipment is constructed so that double insultion is provided between all live parts and (1) the accessible surfaces of the equipment, and (2) all inaccessible parts and surfaces that are conductively connected to the accessible surfaces of the equipment.

Under certain conditions, reinforced insulation systems are acceptable when applied to brushcaps; brushholders; commutator and end turns of armature winding switches; power supply cords; and internal wiring.

Power supply cords for double-insulated tools shall be jacketed and shall not include a grounding conductor.

"Double insulated" or "double insulation" must be permanently marked on the tool. In addition the double insulated symbol (a square within a square) may be used.