Optimized Protective Clothing Keeps Workers Cool and Comfortable

When working in environments of extreme heat, your clothing and its materials matter for your comfort and safety.

• By Jake Hirschi
• Jun 01, 2020

What’s the hottest you’ve ever been—when you were so hot that you were uncomfortably drained of all your energy, battling exhaustion with sweat soaking through your clothes? It might have been during an especially intense workout, or a hike up a mountain or maybe even when doing difficult yardwork on a hot summer day.

Now think about the clothes you were wearing, and how they may have helped mitigate the heat and sweat. If you were working out, you likely were wearing performance sportswear, which is designed to wick moisture away from your body and utilize an evaporative effect to lower your body temperature. If you were hiking, many pieces of outdoor wear have ventilation panels built in to create channels of airflow through the garment. On that hot summer day working in the yard, you likely had a hat and sunscreen on and perhaps a long-sleeved shirt to protect you from the direct rays of the sun.

Now think of doing that same workout, hike or yardwork while wearing a multi-layer PPE ensemble. First, you have a flame-resistant base layer next to skin. Then add a FR-greens coverall and an aluminized jacket and bib. Finally, throw on an aluminized hood with a face shield. Imagine doing the workout, hike or yardwork weighed down by these heavy layers—albeit layers that will protect you from severe injury and burns, but are not optimized for comfort, dexterity or keeping you cool. The amount of discomfort you would feel just went to an entirely different level!

Why would anyone do this?

Real Superheroes Wear PPE

Extraordinarily fit and dedicated firefighters participate in the FDIC 9/11 Memorial Stair Climb every April, an event held in conjunction with the FDIC Tradeshow in Indianapolis to honor and remember the FDNY firefighters who selflessly sacrificed their lives to save the lives of others. The men and women who participate suit up in their full firefighting gear and climb the equivalent of 110 stories in Lucas Oil Stadium, symbolically scaling the height of the World Trade Center. After completing their climb, they are emotionally and physically exhausted, but are humbled and proud to have paid a noble tribute in remembrance of true heroes.

Most of us will never know what it is like to perform such an extreme task while wearing heavy and restrictive gear. But there are industrial vocations that require wearing multiple layers of clothing and equipment to protect against extreme heat and exposure to dangerous thermal hazards each and every day.

Take Working in a Steel Mill, For Example

Aluminum and copper furnaces run between 1500- and 1700-degrees Fahrenheit, and steel furnaces run at temperatures above 3000 degrees Fahrenheit. The PPE worn in these environments must not only shield workers from the potential molten metal splash of these extremely hot materials, but it must also protect against the staggering amount of radiant heat that is generated by the metal and furnaces—all while keeping workers comfortable when performing strenuous tasks. That’s a lot to ask!

Aluminized clothing—coats, jackets, hoods, full-body suits, pants, ankle-high leggings, overshoes and spats—is the PPE of choice for professionals working in molten-metal and high-heat conditions. These PPE pieces’ primary purposes are to protect the wearer from extended exposure to radiant heat, help maintain the wearer’s normal body temperature and shield the wearer from getting burned.

It can be tough to find an option on the market that delivers on all three of these objectives. Mass matters when protecting against extreme heat; the mass in a jacket or fabric provides insulation against the 2900 degrees Fahrenheit steel, the 2000 degrees Fahrenheit molten pulp, or any number of other red-hot liquified hazards. The heavier the outer layer, the more it will insulate against extreme heat.

However, the added weight—combined with the byproduct of restricted movement—can cause the wearer to expend more energy in doing their job, increasing the potential for heat-stress injuries and fatigue while also reducing productivity. Lighter-weight alternatives are typically used solely for radiant heat protection and provide little resistance to molten metal splash.

Reducing the potential for heat-stress while delivering sufficient protection against molten metal splash and radiant heat exposure is the goal. Protective fabric and clothing manufacturers have been challenged with developing lighter-weight (between 12 to 14 ounces per yard squared) aluminized fabrics able to pass the ASTM F955 pour test while improving comfort, reducing heat stress and increasing productivity. Using fabrics constructed of inherently non-flammable fibers is essential, as they easily pass the ASTM F955 pour test, protect against molten metal splash and will not burn, melt or ignite.

These fabrics provide maximum temperature resistance. Ideally these fabrics should be lightweight and maintain their flexibility even after being aluminized, enhancing the wearer’s comfort and productivity.

But no matter their weight or flexibility, almost all aluminized fabrics face the same challenge: the aluminum film on the outside of the fabric is a solid layer, so it is non-breathable.

Breathability Breakthrough

The latest innovative technology in developing aluminized apparel combines non-flammable protective properties with maximum comfort and breathability.

In this unique aluminized PPE solution, a non-woven felt is the base fabric on which layers of hydrophobic and hydrophilic fibers are added to repel and pull moisture away from the body. The moisture escapes through a perforated aluminum surface with thousands of tiny holes. The airflow and water evaporation, after seeping through the holes, has a dramatic cooling effect.

While the holes are small enough to allow air permeation, they are not large enough to significantly impact the level of radiant heat protection that the outer layer of aluminum provides. Likewise, when exposed to molten metal splash, the holes are small enough and the molten metal splash is hot enough that the holes seal when hit with the molten substance.

Keeping Your Cool

Just like performance sportswear helps keep you cool and comfortable, your PPE should keep your most essential workers cool and comfortable in demanding circumstances. Just as performance sportswear becomes standard in the gym, so should the best-option aluminized apparel for protection and comfort become standard in the workplace.

This article originally appeared in the June 2020 issue of Occupational Health & Safety.