On the horizon: Is an “active thermal liner” in your PPE future?

By Battalion Chief Henry Costo, Philadelphia Fire Department — for LION Connects

Historically in the fire service the measure of PPE quality and performance has been thermal stability. Materials such as PBI, Kevlar, Nomex, PBO, etc. were all developed to withstand changes during exposure to heat and flame. Indeed, most of the current standards-related testing has been designed to ascertain whether or not a fiber, fabric, composite, etc. possesses the required thermal stability.

Recently, however, scientists at DuPont have taken a completely divergent approach to the issue of the thermal stability of turnout liner materials. They did so by inventing a liner material possessing engineered and controlled thermal instability. This less-thermally-stable material can now be integrated into a composite turnout system, allowing for selective, and situationally appropriate, performance benefits.

The new “active” liner, which DuPont calls Nomex On-Demand, is designed to respond, i.e. expand or thicken, when the temperature of the material reaches 250 degrees F. Theoretically the activated/expanded thermal liner should provide enhanced thermal protection during situations when firefighters face the greatest potential for sustaining burn injuries.

DuPont believes that it has created a thermal liner material that’s thin, breathable and flexible under ordinary operating conditions (providing routinely high total heat loss/THL), but which is capable of providing enhanced thermal protection (increased thermal protective performance/TPP) during emergent circumstances.

Keep in mind, that not even its developers believe this new material to be a PPE panacea. It’s simply intended to be another tool in the PPE toolbox. In addition, the material is so new that it has yet to be truly tested under field conditions. Its actual performance capabilities and limitations have yet to be determined and questions remain to be answered.

  • Will the new material best be used as part of a complete thermal liner or will its true value be realized through selective reinforcement applications?
  • Once activated, what effect will an expanded liner have on overall THL and wearer comfort?
  • How will the liner system perform when it’s wet?
  • What durability will the liner material possess?
  • How receptive will turnout manufacturers be to the new liner material?
  • How will these manufacturers integrate the new material into their existing liner systems?
  • What is the optimum orientation of the material within a composite system in order to expand where and when it is needed?
  • What will the inclusion of Nomex On-Demand add to the price point of existing turnouts?

Despite these and other yet-to-be determined limitations and lingering questions, there’s NO question that this novel product shows great potential to improve the protective performance of turnout gear.

The concept of selectively increasing TPP only when needed (emergent circumstances) in order to maintain comfortable THL levels at all other times (routine operations) is exciting to say the least. Assuredly, the Philadelphia Fire Department will be among the first to field test garments incorporating this new technology. Report to follow.

(Editor’s note: Battalion Chief Henry Costo is the safety officer for the Philadelphia Fire Department and serves as chair of the safety committee for the International Association of Fire Fighters Local 22. He’s served with the Philadelphia FD for 35 years.)

For more on this topic, you can read Chief Costo’s recent piece in the January 2010 issue of FireRescue magazine.