Article Archive
Aging Ensembles
DuPont participates in performance study on used turnout gear
Vol. 27 Spring 2012

NFPA 1851 now requires that all elements of the protective ensemble for structural and proximity firefighting be retired 10 years after date of manufacture, including helmets, gloves, coats, pants, hoods, and boots. That gear might not be worn out so much as technically obsolete, said DuPont PPE garment specialist Richard Young.

“Would you risk having to go out and fight a fire if they didn’t have the best technology?” Young said. “That technology changes every cycle.”

Working for DuPont’s Applications Research Group, Young is active in developing materials and technologies for emergency response garments. He holds several patents on fabric and component technologies and has worked with various technical committees on developing new thermal test methods.

He also serves on the National Fire Protection Association Technical Committees for Stationwear and Technical Rescue Gear and works with the Technical Committees on Structural and Proximity Gear.

With the next edition due in 2013, NFPA 1851 Standard on Selection, Care and Maintenance of Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting will come under intense review in the coming months.

Although the 10 year cycle for PPE was established in the 2008 version of NFPA 1851, Young said he still encounters resistance to the concept.

“You sell them a new set of gear,” Young said. “Since nobody likes to look like a rookie, they keep using the old gear and keep the new stuff as a spare. The problem is that after 10 years, used or not, that gear is out of compliance with NFPA1851.”

DuPont participated in a recent study conducted by the University of Kentucky on the performance of used turnout gear, he said.

“A lot of departments are complaining that retirement after 10 years is too soon,” Young said. “A lot of work is being done to understand fabric performance, including moisture barrier performance. Some metro departments may wear their gear out in four to six years, while other departments without as many calls may find that their gear lasts longer.”

As much as it rubs firefighters the wrong way to throw away PPE before it completely wears out, establishing a 10-year cycle helps responders keep pace with available improvements that can prove to be life saving, Young said.

“Look at where 10-year-old gear is today,” he said. “Regarding breathability, rather than the required total heat loss of 205, you would have a minimum breathability of 127. You wouldn’t have the reinforcements of the shoulders or the knees that give you added protection. You would not have the drag rescue device which is standard on every set of gear now.”

Young is a technical expert on both Nomex® and Kevlar®. Regarding Kevlar®, DuPont announced the start up of its $500 million Cooper River, SC, Kevlar facility in October. The facility increases overall global production capacity for Kevlar by 25 percent and is expected to grow 40 percent in the next two years.

“The strength-to-weight ratio of Kevlar® is roughly five times stronger than steel on an equal weight basis,” Young said. “It has very good flame durability.”

As for Nomex®, DuPont announced in January that it will discontinue supply of 200 denier to 1,600 denier (a measurement used to identify the fiber thickness of the individual threads in cloth) Nomex® natural filament yarns, and replacing it with various alternatives, most based on Kevlar® filament for use in fire service applications. 

“This product is typically used in some sewing threads, low friction facecloths and specialized outer shells,” the DuPont announcement states. “This discontinuation of supply will not affect the broader Nomex portfolio of products used for fire service garments.  It will leverage our investment in Cooper River and allow for an improved long term supply position for filament-based solutions to these important fire service applications.”

Historically, the push has been to afford firefighters more protection, i.e, greather thermal insulation, Young said. Firefighters too often make the mistake of testing the limits of that thermal insulation by pushing deeper into the fire.

“Eventually, something fails,” Young said. “There have been a half dozen cases where the SCBA masks have failed and firefighters died because, typically, the polycarbonate face piece has a melt temperature of 300 degrees Fahrenheit.”

The firefighter, encased in greater thermal insulation, may not be aware that the surrounding heat has built to that point, he said.

“When you get more and more thermal insulation in your garment you don’t feel the heat,” Young said. “You can stay in the event much longer. But, suddenly, as the heat flux begins to damage the face piece material, firefighters are losing that critical protection.”

Once the face piece is compromised, the firefighter loses precious breathing air, he said. The lungs are exposed to hot gases and toxic fumes.

“So there is an effort in NFPA to try and understand how the system should work as an ensemble,” Young said. “The SCBA should be the last thing that fails in an ensemble rather than the first thing.”

As for the rest of the ensemble, firefighters too often have a misconception of how much heat their gear can really take, he said. “Why did I get burned when my gear did not fail?” they ask.

Essential to NFPA 1851 is the thermal protective performance (TPP) test. It predicts the amount of thermal protection a flame-resistant fabric would provide if exposed to a flash fire. The TPP value is defined as the exposed energy on the outside of the fabric necessary to have enough energy to pass through the fabric to cause the onset of a second-degree burn if a person is wearing the fabric.

The NFPA minimum requirement is a TPP rating of 35, which equates to 17½ seconds until second degree burns occur in a flashover situation.

“Firefighters are rarely in the fire itself,” Young said. “Usually the fire is above your head while you’re on the ground. Rarely do you enter a flame environment unless it is a rescue or escape event.”

The higher the TPP value, the more protective the fabric, Young said. However, TPP is a short endurance test measured in seconds.

“If you look at where Nomex, Kevlar and PBI break down, you’re talking about 700 to 1200 degrees Fahrenheit,” Young said. “At what heat does your skin break down? The material has gotten better but you will still be burned at 135 to 140 degrees Fahrenheit.”

Eventually, as the garment absorbs the energy in the fire fighting environment, it becomes as great a hazard as the fire, he said.

“If you enter an environment that is 300 degrees, the material will not break down,” Young said. “You won’t get any discoloration or charring, but after five or ten minutes that garment reaches 300 degrees because everything goes to thermal equilibrium. That means you will suffer some body burn even with no damage to your gear.”

Calculating the minimum level of protection that firefighters need must also take into account the flammable material that surrounds them, Young said.

“New studies conducted by Underwriters Laboratories indicate that the predecessors of today’s firefighters might have seven to 10 minutes before a room flashed over, based on the use of wood, leather and other materials,” he said. “In a modern room using a lot more plastics and synthetic materials, that flashover occurs within three to four minutes.”

Unfortunately, that coordinates with the ideal target response time most fire departments set as a goal, Young said.

“You’ve got to be prepared to understand the new hazards that you’re facing today with modern furnishings as opposed to 10 or 15 years ago,” he said.

Just as important, recent NFPA standard revisions have addressed heat stress issues, i.e., the breathability of the garment, Young said.

“There has been some talk about reducing the level of TPP from 35 to something lower,” he said. “When I first started about 15 years ago, TPP was in the mid 40s and 50s. Everybody wanted the maximum protection. Now everybody is making the thinnest, lightest weight systems they can.”

Today, turnout gear is treated as a total system, Young said.

Watch for opportunities to respond to the 2013 version of NFPA 1851. Give the committee your “real world” input and vision of how to make the total turnout gear system safer and functional. Most of all, inform your responders of the limitations of their gear and equip safety officers with facts on exposure limits. Plan for PPE replacement rotations by response units and let new gear users share benefits and challenges to guide your next purchase decision.                         

 
 

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