Flame-resistant (FR) clothing can increase the chances of survival and decrease the need for medical treatment and the chances of subsequent infections. It can help preserve the quality of life of a worker exposed to an electric arc flash.

Wearing ordinary clothes, especially synthetic fabrics like nylon, in an arc flash may make injuries worse than if the skin was not covered at all. Denim jeans and jackets, cotton shirts, cotton/synthetic T-shirts, sweatshirts, fleeces or nylon jackets are fuel sources that ignite, burn and frequently melt onto the skin. The heavier the weight of the fabric, the more fuel there is to burn. The explosion may be over in less than a second, but non-FR clothing may keep burning. It takes just three seconds to sustain third-degree burns.

NFPA 70-E

To help workers understand burn dangers more easily, the National Fire Protection Association assigns a 0-4 number to hazard/risk categories representing the danger level. The minimum hazard rating for arc flash puts the burn exposure at 4 cal/cm2, which is a NFPA 70-E “Category 1 Hazard” rating. Calories per centimeter squared is a number identifying the amount of energy that can be delivered to a point at a particular distance from an arc flash. Once this value is known, the ATPV rating of the PPE required for work at that distance from the potential flash hazard is also known. FR apparel must be worn for the “Category 1 Hazard” level.

When selecting an FR garment for electric arc hazards, look for labels that show the arc rating as required by the ASTM F1506 Standard for Flame Resistant Clothing. The standard has two basic requirements:

• A sample of fabric must self-extinguish with less than 2 seconds after flame and less than 6” char length according to ASTM Test Method D6413.  This flammability test applies to an initial sample and after 25 washes/dry cleanings.

• The fabric must be tested for Arc Thermal Performance according to ASTM Test Method F1959. The results of the Arc Thermal Performance testing must be reported to the end user as an Arc Rating on a garment label.

• Different colors of the same fabric do not need to be tested separately.

A garment that meets ASTM F1506 complies with OSHA 1910.269, NESC and NFPA 70E. ASTM F1506 is a pass/fail standard with requirements for reporting information not considered for the pass/fail criteria.  All garments that meet the requirements of ASTM F1506 must be labeled with a tracking code, a statement that the garment meets the requirements of ASTM F1506, the manufacturer’s name, size information, care instructions, fiber content and the arc rating. 

REFERENCES

https://www.osha.gov/SLTC/etools/electric_power/ppe_flameresistantclothing.html

https://safetyequipment.org/knowledge-center-items/ppe-changes-for-arc-flash-continue-to-drive-market-2/

http://www.tyndaleusa.com/index.php/component/content/article/16-fr-safety-library/faqs/116-fr-basics-faqs#What%20is%20a%20hazard%20risk%20category