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Nomex coverall affordably protects soldiers from fire risks

Nomex coveralls sent to a group of combat support soldiers participating in Operation Enduring Freedom could be the beginning of affordable flash-flame protection for all soldiers.

Seventeen sets of the disposable garments were sent from the U.S. Army Soldier Systems Center in Natick, Mass., in July in response to a request in June that included flame-resistant clothing. The sage green, commercially-available coveralls were selected because of their ability to reduce burns from 88 percent to 8 percent at a three-second exposure on an instrumented manikin when worn over a Battle Dress Uniform (BDU), T-shirt and briefs.

Commercially-available Nomex coveralls
Commercially-available Nomex coveralls, originally designed for industrial workers, use a simpler manufacturing process to help lower the cost. Seventeen sets were sent to soldiers participating in Operation Enduring Freedom.

“The problem is that soldiers are going to be at risk of burns from accidental flash fires because they don’t have the right clothing,” said Carole Winterhalter, a textile technologist with the Individual Protection Directorate, who responded to the request.

Furthermore, the coveralls cost $25 a set. Fitted over a regular BDU, the cost totals about $80 vs. $180 for a Nomex aircrew BDU.

Soft, lightweight and air-permeable, the coveralls are made from a blend of 92 percent Nomex, 5 percent Kevlar—both flame-resistant fibers developed by DuPont—and 3 percent nylon.

Cost savings are credited in part because the non-woven material is made by direct fiber-to-fabric manufacturing that removes the steps of yarn spinning and fabric preparation yet retains high tearing strength. Another reason is the simple garment design with no cuffs and minimum stitching. If the sleeves or legs are too long, a soldier can snip off the extra length with scissors.

Army aviators and tank crew members are the only servicemembers authorized to wear flame-resistant clothing, which is made mostly from woven Nomex fabric. The fiber chars instead of melts and gives durable flame protection for the life of the garment. Although well-liked, Winterhalter said the clothing is too expensive to issue to every ground soldier.

Nomex coverall
An instrumented manikin wears a Nomex coverall before flame testing.

A team of scientists at Natick has been working on a five-year research and development program to establish flame and thermal performance requirements for military clothing systems, demonstrate a flammability test methodology that simulates military flame and thermal hazards, and finally come up with an affordable protective clothing system for infantrymen.

“The thought was that everything from the skin out had to be flame-resistant,” Winterhalter said. “We’re finding that’s not necessarily the case.”

Flames engulf manikin
Flames engulf the manikin for three seconds.

Depending on the application, only the outer layer needs to be flame-resistant.

“Based on laboratory testing, we found that just the insulation—the thickness of the material—provides thermal protection. Each additional clothing layer adds insulation and increases protection time,” Winterhalter said.

In an environmentally-controlled chamber, the scientists used an instrumented manikin equipped with 122 sensors that can determine the percentage of second and third-degree body burns on everything except the hands and feet. In testing, it simulates the effects of flash fires soldiers may be exposed to on the job.

Charred Overall
The charred coverall shows little damage from the flames.

The coveralls now supporting the soldiers were designed for industry. Not intended for fire fighting, they passed National Fire Protection Association standards for industrial workwear when independently tested by the Underwriters Laboratory. Winterhalter said it’s a limited-wear garment with low-abrasion resistance and prone to pilling. For an industrial worker, it may last 10-12 washings before being disposed.

“We’re hoping to get feedback from the soldiers and use it in conjunction with an ongoing development effort to come up with a military-specific version,” she said.

Intact Battle Dress Uniform
Pulling off the coverall exposes an intact Battle Dress Uniform.

The military version will have a camouflage pattern, openings to gain access to garments worn underneath, sizing that fits the military population, and an oil and water repellency treatment that may also reduce pilling and enhance durability. Even at double the cost and worn over the BDU, Winterhalter said the system will still be 40 percent less expensive than existing flame protective clothing.

That would meet the team’s final objective of developing a flame-protective clothing system that’s 30-50 percent less expensive than existing Nomex-based systems.

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