Question: Does the use of metal components in FR garments for electrical workers, such as metal snaps and zippers on shirts and coveralls, present a hazard and are they prohibited by NFPA 70E or ASTM F1506?
The only NFPA 70E reference to metal components is in section 130.6 (D) Conductive Articles Being Worn. In there it states, “ Conductive articles of jewelry and clothing (such as watch bands, bracelets, rings, key chains, necklaces, metalized aprons, cloth with conductive thread, metal headgear, or metal frame glasses) shall not be worn where they present an electrical contact hazard with exposed energized electrical conductors or circuit parts.” The main concern here is one of shock although articles like jewelry falling off could cause an arc hazard. Snaps or zipper are not really in the same category but it could be a matter of interpretation.
The reference in ASTM F1506 is in the section 6.1.1 note. It states, “If fasteners or closures, for example zippers, snaps, or buttons, or a combination thereof, are used in a manner in which they are in contact with the skin, they can increase heat transfer and burn injury due to heat conduction or melting on the skin. Fasteners or closures that are used in this manner should be covered with a layer of fabric between the fastener or closure and the skin.” The concern here is if exposed to an arc flash the metal component would transfer more heat and cause more burn injury.
Based on the standards references shown above it does not appear either standard prohibits the use of metal snaps or zippers. There is also a written statement by OSHA in reply to a question about metal zippers in linemen’s clothing relative to OSHA 1910.269. The statement was, “The metal in a metal zipper is not expected to contribute to the severity of injury sustained by an employee in the event an electric arc occurs. Therefore, provided the surrounding materials meets the Apparel Standard, the metal zipper will be acceptable under paragraph 1910.269(l)(6)(iii).”
In addition, our research with industry experts found no known incidents where a metal snap or zipper caused either an electric arc or shock. Plus, sleeve snaps are generally not very large and if the user is working energized their protective gloves typically cover the end of the sleeve where the snaps are found. According to YKK, a major zipper manufacturer, metal zippers, although made of conductive materials, have difficulty creating an arc as they are not continuous metal. Also most zippers have some fabric coverage over the front of the zipper helping to insulate it from contact. By standard, when a garment uses metal snaps and/or zippers they should be covered on the inside so no metal comes in contact with the skin. The bottom line is no standard prohibits the use of metal snaps or zipper and practically speaking they have not been shown to cause problems. However it is up to the individual organization to perform an assessment of their hazard and determine what position they want to take for their garments.