Electrical Arc Flash Clothing

Arc Flash Clothing
Arc flash clothes are critically important to keep workers safe. Statistics show that five to ten times a day, a worker in the United States is injured or killed due to an arc flashing accident [2]. The casualties resulting from these accidents are almost always devastating to the worker involved and to the worker’s family [2]. Perhaps if these workers had been wearing appropriately rated arc flashing protective equipment, the number of injuries and deaths could have been decreased.

What is an Arc Flash?
Let’s start by explaining the electrical phenomenon of an arc flash. The arc flash is the resulting discharge of energy caused by an arcing fault. An arcing fault is the unintended flow of current through a medium not intended to carry the current. What? That just means that the electricity is flowing through something it shouldn’t be; in most cases that result in injury, the medium was the air. The air becomes like a piece of copper, conducting the electricity, only with the air, you can see the massive discharge of the electrons from the discharging element. This is the arc flash. It’s lightning on a smaller, yet a more deadly, scale.

What causes an arc flash? Well, as said above, the cause is an arcing fault. What causes an arcing fault? Many things. The most common causes of an arcing fault are equipment failure, human error (improper placement of tools or improper use of equipment), or the conduction of electricity due to foreign particles in the air (usually metal shavings) [1].

Need for Protective Clothing
What steps can be taken to reduce the risk? NFPA 70E, Standard for Electrical Safety Requirements for Employee Workplaces sets standards and regulations for workers working around energized equipment. NFPA 70E defines necessary steps to be taken to properly prevent serious injury in the event of an arc flash accident. Simply put, NFPA 70E calls that when a worker is within the Flash Protection Boundary (the area where discharged energy is greater then 1.2 cal/cm2) he must be qualified and wearing thermally resistant and arc flash protective clothing. For training, arc flash videos are useful.

Arc Flash Clothing Selection
Picking the right type of arc flash protective clothing is, fortunately, quite easy. First, consult NFPA 70E 2004 Edition table 130.7 (C)(9)(a) to determine to which category of risk a particular activity belongs. Second, consult Table 130.7 (C)(10) to determine what type of clothing/equipment is required based on the category of risk determined. Third, consult Table 130.7 (C)(11) to determine the ATPV (arc thermal performance value) rating needed. Once you have done all this, just go out and find the protective gear that meets or exceeds this rating [3]. One thing to remember when picking the protective work wear is to try and ensure that no skin is exposed. Ensure that the pant legs (if not connected to boots) completely go down to the boot. Also ensure that the sleeves of the protective work wear go down to the hand, leaving none of the arm exposed. And lastly, remember that the head is the most vulnerable part of the body. Don’t forget to complete the arc flash protective clothing with suitable head gear of the same ATPV rating as the rest of the work-wear plus high voltage gloves.

Occupational Safety and Health Administration (OSHA) also has requirments on arc flash clothing, and the ASTM has devised test methods for arc flash protective clothing, including flame retardancy (FR) testing..

Hazard Risk Category	Work-wear Description (1/2/3/4) refers to the number of clothing layers	ATPV Rating cal/cm2
0	Untreated Cotton (1)	n/a
1	FR Shirt and FR Pant (1)	5
2	Cotton Undergarments + FR Shirt/Pant (2)	8
3	Cotton Undergarments + FR Shirt/Pant + FR Coveralls (3)	25
4	Cotton Undergarments + FR Shirt/Pant + Double Layer Switching Coat and Pant (4)	40

When nothing can be done about working within a flash protection boundary, proper arc flash protective clothing needs to be worn. Workers need to remember that arc flash accidents don’t only occur with equipment at high voltage. The majority of arc flash accidents occur with low (120V) and medium voltage (480V) equipment. Workers who wear the proper arc flash protective clothing will significantly reduce the risk of injury or death, should an arc flash accident occur.

Arc Flash Meeting Held
A recent article in NEMA Electroindustry Magazine reported on a meeting that was held to share information on the IEEE/NFPA Arc Flash Research and Testing Project. The meeting was held at NEMA headquarters, and included representatives of NFPA, IEEE, and some NEMA member companies.