Arc flash rated clothing is designed to provide a barrier from heat and flame, to maximize the level of protection and minimize total burn injury and to help provide the wearer with extra seconds of protection to help escape possible secondary explosions or fires in the work area.
Arc rated clothing can increase the chances of survival and decrease the requirement for medical treatment (skin grafts) and the likelihood future infections. PPE can also help maintain the quality of life of an electrical worker exposed to an electric arc flash accident. Arc Flash PPE is not designed to be fire fighting gear; it is worn by electrical workers to help minimize the risk of serious injury caused by arc flash and arc blast explosions.
If electrical workers wear ordinary clothes, (especially many synthetic fabrics such as nylon), an electric arc flash fire accident may actually lead to more serious injuries than if the skin was not covered at all. It has been proven that wearing denim jeans and jackets, cotton shirts, cotton/synthetic T-shirts, sweatshirts, fleeces or nylon jackets actually all become additional fuel sources that continue to ignite, burn and frequently melt onto the skin, even after the actual ach flash has diminished. Also, the heavier the weight of the cotton/nylon fabric worn, the more fuel there is to burn. Remeber, it often takes just a few seconds for an electrical worker involved in an arc flash accident to sustain a third degree burn.
In electric arc blasts, even flame resistant garments can break open due to the extreme energy. Its prudent to wear loose-fitting fr flame resistant layers, with a protective clothing outer layer, and underwear that won’t melt. Suitable flame retardant ppe will help insulate the wearer from heat, resist breaking open, and will not ignite or continue to burn when exposed to a high intensity, short duration explosion and fire.
To help workers understand the burn dangers more easily, the NFPA assigns a 0-4 number to hazard/risk categories representing the minimum arc rating danger level. The minimum hazard rating for arc blast puts the burn exposure at 4 cal/cm2, which is a NFPA 70-E “Category 1 Hazard” rating. FR apparel must be worn for the “Category 1 Hazard” level. When choosing an FR garment to be worn in an arc flash hazard area, look for labels that show the arc rating as required by the ASTM F1506 standard or NFPA 2112.
Examples of such Arc flash rated clothing is more than just shirts and pants. It could include flame resistent hat, face shield, flame resistant neck protection, hearing protection, suit, insulated rubber gloves with leather protectors, and insulated leather footwear.
All ppe must meet the requirements as shown in the latest edition of NFPA 70E "Electrical Safety In The Workplace". PPE, sufficient for protection against the potential for explosion, is required for every part of the body.
100 Percent Cotton: It was not all that long ago that 100% cotton was considered the appropriate ppe when an electrical arc exposure was present. It was considered that 100% cotton provided much better protection than polyester, which is true. However, ppe testing proved that 100% cotton only served to add fuel to explosive energy. It was also proven that the best way to protect a person from being burned was for the person to wear flame restardant clothing.
Flame-Retardant Treated 100 Percent Cotton: One such fabric available today is marketed under the trade name “Indura.” This fabric is made by Westex and is guaranteed to maintain flame retardant performance throughout the life of the ppe. This fabric has an expected wear life of 50 to 75 home launderings. This means that five sets of shirts and pants, each worn once per week, will last 12 to16 months in the range of light- to severe-use conditions.
In Indura-engineered fabrics, the flame retardant chemical impregnated into the cotton fiber core acts as a catalyst to promote the charring of the fabric. This charring actually inhibits additional combustion by greatly reducing the fuel source. The flame retardant chemical acts in the solid phase to produce this charring. The mechanism of action is not based on a gaseous process of extinguishing or “snuffing out” the flame.
It is very important that ppe be maintained in a clean condition to realize their full protection potential.
Flame-Retardant Treated 88 Percent Cotton, 12 Percent Nylon: Previously, it was stated that nylon was an undesirable fabric for electric arc-blast protection. With this blend there is a mechanical type reaction when it is exposed to excessive heat. The nylon melts and essentially fills up the gaps between the cotton fibers creating a more solid defense against the heat source. This fabric is sold under the trade names of “Banwear” (made by Itex) and “Indura UltraSoft” (made by Westex). Both of these products guarantee that the flame retardant performance of the ppe is maintained throughout the life of the garment. One can expect Banwear and Indura UltraSoft to last 18 to 30 months when worn daily and home laundered once per week.
93 Percent DuPont™Nomex® , Five Percent Kevlar, and Two Percent Antistatic Fiber: This long-winded description is most commonly know by its trade name “Nomex IIIA.” manufactured by DuPont™. Nomex IIIA is a lightweight, inherently flame-resistant fiber blend. It does tend to have a higher heat let-through rate. This fabric is available in weaves from 3.3 to 7.5 ounces per square yard. Some weights are available in ripstop and twill weaves. Nomex IIIA has an expected wear life of 30 to 48 months.
Care and Cleaning
A variety of flame-resistant fabrics are available in today’s marketplace. Each fabric has unique wear, comfort, appearance, and durability characteristics. Each of these issues should be considered when making an ppe purchase.
Industrial laundering creates more wear on a garment than home laundering. Also, it has been found that heavy facial growth has a negative effect on wear life of a collared shirt. Additionally, repeated abrasion of any type shortens wear life in the area on the ppe where the abrasion occurs.
Note: Indura ppe should not be laundered with hypochlorite (chlorine) bleach because repeated exposure will break down the finish and is destructive to the fabric and the color. Most flame-resistant fabrics, bear instructions warning against the use of chlorine bleach because it may weaken to the fabric strength and color even if flame resistance is not affected.