Page 28 - Occupational Health & Safety, May 2019

PROTECTIVE APPAREL
The Truth About Heat Stress and FRC
It would be a terrible shame to put American workers at risk of catastrophic or fatal burn injury because of an outdated myth about PPE and heat stress.
BY SCOTT MARGOLIN
24 Occupational Health & Safety | MAY 2019
www.ohsonline.com
As we approach warmer weather, questions around comfort and heat stress become significant for people specifying or wear- ing flame-resistant protective apparel, so it’s important to understand a few basics on the interrela- tionship, if any, to fabric type and weight. Discomfort and heat stress are not used interchangeably. Comfort is an inherently subjective characteristic that cannot be effectively or predictably measured by lab tests or judged across a desk, and is a nuisance issue. Heat ill- ness, however, is a measureable physiological condi- tion with potential medical consequences, and it is (perhaps surprisingly) unrelated to comfort.
Comfort
Studies have clearly shown the primary factors cor- relating to comfort are choice, fit, and brand/style, notfabric.Nosinglefabricproperty,suchasweight, breathability, wickability, or the way the fabric feels, or “hand,” correlates to comfort. And combinations of three or more properties are only marginally more predictive. Despite popular perception, comfort is not linked to weight; the significant majority of wear test participants consistently rate many garments as more comfortable despite higher weights.
Combining properties, such as light weight and high breathability, for instance, are meaningless in the absence of other properties (a window screen has ex- cellent numbers in both categories). These only begin to matter when combined with a soft hand and excel- lent moisture wicking, and even that data ignores the Big Three factors of choice, fit, and brand/style. Com- fort differs greatly from person to person and from day to day, and generalizations cannot be made from any single property. For much more detail on comfort and FRC, please refer to the article “Is Comfortable FRC an Urban Myth?” on page 30 of this magazine’s March 2019 issue.
Heat Stress
Heat illness is a potentially serious health concern, not a perception issue; it is a series of measurable and increasingly dangerous physiological affects resulting from the overheating of the body and the cascade of effects on organs and systems. This over- heating can be caused by hot and/or humid ambient conditions, or by metabolic heat generated by hard physical work, or both. Heat stress has a number of stages, and timely and appropriate intervention can stop or reverse the progression.
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