Heat stress Protective clothing

FR/AR clothing and heat

Does flame-resistant/arc-rated clothing contribute to heat stress?


Responding is Scott Francis, technical sales manager, Westex: A Milliken Brand, Chicago.

It’s a hot day on the jobsite and you’re starting to feel lightheaded, overheated or even nauseated. Are you experiencing symptoms of heat stress or is it simply discomfort?

Not all discomfort is a sign of heat-related illness, and heat stress isn’t necessarily caused by personal protective equipment. That’s why it’s important that workers understand their environment, the task at hand and the appropriate fabric to wear. This can help them better evaluate whether something is a comfort issue or a sign of heat stress. Once they know the difference, they can take appropriate steps to amend the situation – whether that means ensuring they’re wearing PPE correctly, choosing different fabrics, or monitoring their well-being and opting for a rest or water break.

Being informed is crucial to protecting lives, so let’s define the difference. Comfort is an inherently subjective characteristic that can’t be effectively measured by lab tests. Heat stress, on the other hand, is a specific and potentially serious illness caused by a series of increasingly dangerous physiological effects resulting from overheating of the body and internal organs. This can be caused by hot and/or humid conditions, sun exposure, a lack of moving air, the intensity of labor and, in some cases, heat-trapping PPE.

Contrary to popular belief, clothing isn’t a significant factor in causing heat-related illnesses. This is true for flame-resistant/arc-rated clothing and non-FR clothing. More often than not, if you’re wearing single-layer, breathable FR clothing and feeling hot, it’s tied to comfort. If you’re wearing multiple layers, there’s more of a risk for heat stress – and wearing fabrics that are breathable and moisture-wicking is key to reducing that risk.

The science behind how our bodies shed heat can help explain. We all have two ways of cooling ourselves: radiation and evaporative cooling. Radiation is the movement of heat from a hotter area (the person) to a cooler area (the atmosphere). Of course, as the ambient temperature approaches that of the person, this ceases to be effective. That’s when evaporative cooling (also known as sweating) kicks in. When sweat is evaporated off your skin, it takes heat with it. As long as the clothing being worn allows radiant heat to escape and sweat to be evaporated, the body’s cooling mechanisms will continue to function as they should.

The science makes it clear: Rather than being a cause of heat stress, FR/AR clothing can actually be part of the solution. With the right fabrics, PPE can not only be standard-compliant, but help you stay cool, comfortable and protected on hot days. Start by specifying light-colored fabric that is designed for the environment and potential hazards at hand. Think short sleeves are the only solution? Think again. Long sleeves are often considered better at preventing heat stress because the sun is a radiant heat load and long sleeves shield the wearer.

If the job requires multiple layers of PPE, look for textiles that are engineered to work together to protect and perform.

Innovation in FR/AR fabrics has advanced far beyond the restrictive options of the past, when PPE was often non-sweat wicking, heavy and inflexible. Today, the significant majority of FR/AR garments made in the United States are virtually indistinguishable from non-FR performance garments in design, style, fit, weight and lasting comfort.

In addition to specifying more breathable, comfortable FR/AR fabrics and ensuring those garments are worn properly, proactively focusing on self-care is critical to preventing heat stress. Monitor your vital signs and sweat levels, take appropriate breaks, find shade when you can, and stay hydrated throughout the day. In fact, the OSHA awareness campaign on heat stress prevention boldly promotes “Water. Rest. Shade.”

Ultimately, if a worker’s PPE is not right for the task or is worn incorrectly – working against them and not for them – they’ll be less likely to wear it. PPE can only protect if it’s worn – and worn properly. Equipping your team with innovative FR/AR garments that are safety standard-compliant and comfortable will not only transform common clothing misconceptions regarding heat stress, but the FR/AR clothing can actually give the wearer a preventive advantage when they need it most.

Editor's note: This article represents the independent views of the authors and should not be construed as a National Safety Council endorsement.

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