by , on August 3, 2010

Question: Can we use metal snaps on shirts for NFPA 70E?  Our traditional shirts have snaps and we are wearing arc rated t-shirts for daily wear then putting on arc rated long sleeved shirts for energized work.

 Answer:  Good question! This opens up how standards work and are often misinterpreted.

 NFPA 70E says 130.6 (D) “Conductive articles of jewelry and clothing (such as watchbands, 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.”

 ASTM F1506 which is cited by NFPA 70E for clothing requirements says the following:
“6.1.1 NOTE 4-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 onto 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 fabric used for this purpose shall meet the requirements of this performance specification.” ASTM F1506-08
 
The issue in NFPA 70E is shock.  The issue in F1506 is arc flash. Metal can conduct electricity but small snaps have little chance of doing this (not NO chance). Companies may have whatever policies they wish and some manufacturers do not offer metal snaps.  Others cover the snaps but many offer either option.  This comes back to risk.  Very few companies regulate metal belt buckles but most regulate jewelry.

 Jewelry can fall off. Conductive aprons etc. cover large areas of the body with conductive materials.  This is a matter of interpretation and our internal consensus was that snaps would not be necessarily prohibited.  We have decided to take this to a survey and report the results next month.
 
OSHA, NFPA nor ASTM have any official mentions of metal snaps so the choice is still one for the market.

 We know of no incidents where metal snaps caused an arc or shock.  In Randy Feltholder’s accident, which was a medium voltage shock, the metal rivets in his jeans conducted the electricity better and caused deeper burns in that area. So even small amounts of metal aren’t NO risk. But metal snaps will probably not cause an arc or shock if all other PPE is worn correctly and proper safe work methods are used.

 Some manufacturers cover the snaps with a plasticized dielectric covering to allow the convenience of snaps and further lessen the risk of shock.


Hugh Hoagland
About author:

Hugh Hoagland is the foremost tester of clothing and PPE exposed to electrical arcs and is an arc flash expert. Read more about Hugh.


5 Comments on "Burn Up the Myth: Metal Snaps on Arc Rated Clothing in ASTM F1506 and NFPA 70E?"

Manufacturer to Hugh@e-Hazard.com - 4 August 2010 Reply

A thought after reading your article on metal snaps. Isn’t it true that the most likely snaps to create a shock or arc hazard are the ones on the sleeve cuffs? If this is the case, they should be covered by the rubber gloves if the person is working hot.

    Hugh Hoagland
    Hugh Hoagland - 4 August 2010 Reply

    I agree. This is one of the reasons it doesn't give me too much heartburn. The Poll is currently against it though! We'll see what a few more days says. It went in the newsletter and over 2000 have opened it but only 71 replied to the poll. We are at 59% against the snaps and 37% for. Several said it should ONLY be done in less than 600V.

Michael Reedy - 24 August 2010 Reply

First, you should do all that you can to de-energize the circuit before working on it. Second, if you have to work on it hot, you better have all the proper PPE on before you start. Third, I just looked at my PPE and the snaps have a layer of fabric between myself and the inside of the snap. I personnally don't see a problem with snaps.

    Hugh Hoagland
    Hugh Hoagland - 30 August 2010 Reply

    If some one is wearing rubber gloves, the snaps don't give me much heartburn on LV. On HV I'm a little more concerned. I don't know of any major issues from snaps covered on the back. Our poll has about 60/40 against at this point. We'll see if this holds but we have about 80 responding.

Hugh Hoagland
Hugh Hoagland - 7 December 2010 Reply

Metal on clothing has been involved in one incident I know of. The incident was a high voltage contact in which the metal rivets in a pair of non flame resistant blue jeans made burns deeper from electrical flow through the rivet. This was not covered on the backside of the rivet like ASTM F1506 requires. Metal snaps have advantages as do metal zippers. Wear life etc. The chance that they will increase injury is still a compelling argument to allow their use. Covering on the outside with a dielectric cover like some do is a good design. Just trying to keep things realistic.

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