‘The 269’
Best Practices for Arc Exposures and Use of FR Clothing
BY CHRIS SANFORD

Electric arcs pose some of the most serious safety hazards for electric power industry workers. Arc flash hazards include temperatures that can be hotter than the surface of the sun, hot gases, an intense pressure wave from explosion, and shrapnel from vaporized and molten metal particles. When exposed to an arc, the clothing the worker wears may play a large role in the severity of the potential injury.

The 269 Standard

According to 29 CFR 1910.269(l)(6), workers are prohibited from wearing clothing that, in the presence of an arc, can potentially increase the extent of injury; that is, if the clothing would ignite and continue to burn, or if it melts on the skin. Thus, workers are generally prohibited from wearing clothing materials made entirely of or blended with synthetic materials such as acetate, nylon, polyester or rayon.

Clothing made from 100 percent cotton or wool may be acceptable if its weight is appropriate for the flame and electric arc conditions to which a worker could be exposed. As heat levels increase, these materials will not melt, but they can ignite and continue to burn.

The amount of heat required to ignite these materials is dependent upon a number of factors, including the weight, texture, weave, and color of the material.

This type of clothing does not comply with the “269” standard if it can ignite (and continue to burn) under the electric arc and flame exposure conditions found at the workplace.

The standard calls for use of flame retardant clothing rated for particular heat exposures. In response, the FR clothing industry has developed a heat energy rating system for FR fabrics. To identify the appropriate FR clothing to use, the heat energy, measured in calories per square centimeter (cal/cm2), to which workers are exposed needs to be calculated.

Once you’ve chosen your FR clothing, it’s important to note that flame retardant clothing that has been contaminated with grease, oil, solvents, or other flammable substances should not be used because such contamination greatly reduces its effectiveness. See ASTM F1449-01, Standard Guide for the Care and Maintenance of Flame, Thermally and Arc Resistant Clothing.

But there is another issue manufacturers of flame retardant clothing are dealing with, and that’s heat stress.

Mental and physical exertion increases the body’s core temperature, and increased blood circulation and the production of perspiration cool the body down. This cooling process can be disrupted due to improper heat and moisture management leading to problems with concentration, fatigue, muscle cramps, difficulties breathing and ultimately heat stroke.

In a technical bulletin, OSHA says, “Operations involving high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects or strenuous physical activities have a high potential for inducing heat stress in employees engaged in such operations; those that require workers to wear semi-permeable protective clothing are also likely to cause heat stress among workers.”

A moisture management and breathable underwear fabric can lead to a reduction in risk from this danger. The fabric has to be designed to reduce fatigue caused by heat stress, while also increasing fire protection by not increasing the severity of burn injury beyond the initial assault.

“Many FR fabrics don’t move moisture,” said Diane Basso, president of Wickers Performance Wear Inc., a maker of flame retardant, moisture-wicking clothing and underwear. “Moisture movement is inherent in the fibers we use. But it also has to be comfortable because it's worn next to your skin. We could not use anything that is not soft.”

She said the combination of FR rayon and fine merino wool offers functionality. The performance and efficiency of the wearer improves significantly when the comfort of the protective undergarment is enhanced. Moisture absorption, combined with the proven ability of wool to move perspiration, quickly results in an all-natural process known as evaporative cooling. These fiber properties make it possible for our FR fabric to significantly reduce the risk of heat stress and heat stroke.

The combination of fine micron wool and FR rayon fibers presents an answer to solving the problem of fatigue due to heat stress for garments worn next to the skin.

The fibers used and the resultant fabric are fire retardant, non-toxic, will not melt or stick to the skin and is free of static electricity. It will not accept nor retain body odors. The fabric can be laundered with other fabrics and is capable of long wearing life under tough environmental conditions. The more it is washed and worn the more its comfort increases.

Basso said, “the development and research activities of Wickers’ FR underwear fabric, which started in 2003, was in response to the growing number of TV images of large forest fires in the Western U.S. But, before we could market this product to the outdoor market, the need for an FR underwear fabric for Special Forces took precedence.”

The company has since provided 30,000 FR underwear and T-shirts to the military without a single complaint about comfort or performance. FSM