EEI SOPD Practice Test 13

Arc-Flash Clothing Explained

¹An arc flash is a burst of heat and light that occurs when electric current jumps through the air between conductors or from a conductor to ground. In a fraction of a second, an arc can become several times hotter than the surface of the sun. Most arc-flash injuries are burns rather than shocks, and the worst burns often happen when ordinary clothing catches fire and keeps burning after the arc is over.

²Arc-rated clothing is made from fabrics that resist catching fire and stop burning once the heat source is gone. Each garment carries a label showing its arc rating, a number in calories per square centimeter. The rating describes how much heat energy the fabric can take before a second-degree burn to the skin beneath it becomes likely. Before a task, the worker compares this rating with the heat energy the task could produce. The clothing's rating must be equal to or greater than that amount.

³What a worker wears under arc-rated clothing also matters. Many synthetic fabrics, such as some nylon and polyester blends, melt when heated and stick to the skin, deepening a burn. Undergarments should therefore be made of natural fibers such as cotton or of arc-rated material.

⁴Arc-rated clothing protects only when it is in good condition and worn correctly. Sleeves are rolled down and fastened, and shirts are closed so that no skin or meltable fabric is exposed. Clothing soaked with oil or grease can burn, so stained garments are cleaned or replaced before use.