Question: Can I wear poly blends under arc-rated clothes?
Answer: Your company requires that you wear 40 cal/cm2 suits for all work requiring arc rated clothing. This is usually a sign of a company which has not done a proper hazard assessment or who has a preliminary program.
A quality arc hazard assessment doesn’t over-simplify the clothing to the worst case scenario. It does however attempt to protect all workers from the hazards.
We understand that your normal work clothing (daily wear) consists of a poly-cotton shirt and pant and you are worried that wearing this type of clothing under arc-rated clothing might be a hazard. Based on clothing tests performed by ArcWear.com, we agree that the combination of poly-cotton blends under arc rated clothing may expose workers to serious burns from possible clothing ignition from a tracking arc or breakopen of the flash suit.
NFPA 70E is very clear about this issue as is NFPA 2113 for flash fire exposure.
Article 130.7(C)(12), , entitled “Factors in Selection of Protective Clothing” states, “Clothing and equipment that provide worker protection from shock and arc flash hazards shall be utilized. Clothing and equipment required for the degree of exposure shall be permitted to be worn alone or integrated with flammable, non-melting apparel.” (Emphasis mine)
NFPA 70E Article 130.7(C)(14), entitled, “Clothing Material Characteristics” goes on to say, “Clothing made from flammable synthetic materials that melt at temperatures below 315°C (600°F), such as acetate, acrylic, nylon, polyester, polyethylene, polypropylene, and spandex,either alone or in blends, shall not be used.” (Emphasis mine.)
NFPA 70E reiterates this in Article 130.7(C)(15), on page 36, entitled, “Clothing and Other Apparel Not Permitted”states “Clothing ….made from materials that do not meet the requirements of130.7(C)(14) regarding melting, or made from materialsthat do not meet the flammability requirements shall not bepermitted to be worn.”
So, We recommend you use arc-rated undergarments or natural fiber garments UNDER arc flash suits in potential arc hazards.
We further recommend using an arc-rated daily wear, either HRC 1 or HRC2 level and add a flash suit to that. The simplified two category arc rated clothing system as described in NFPA 70E Annex H, page 83 is also a good option. Keep in mind, you will be using the tasks as listed in Table130.7(C)(9), page 30 of NFPA 70E. Therefore, your power distribution system short-circuit current capacities and fault clearing times need to meet or be less than as noted in the table notes.
Some companies have helped with heat stress by purchasing an arc flash suit designed to work WITH their daily wear to provide the required protection to avoid OVERDRESSING for the hazard. One plus of this approach is less heat stress and probably a clothing savings. We prefer arc rated daily wear when possible. For those rarely exposed to arc flash, natural fibers are allowed by the standard.
Al Havens & Hugh Hoagland