High Performance Thermal Liners

What do High Performance Thermal Liners have in Common with the Apparel Worn by LeBron James, Usaine Bolt, and Tiger Woods?

Before we get to that, let’s establish a few things:


1)  What is a thermal liner?
A firefighter’s turnout gear is made from multiple layers of high performance materials to protect from a range of physical,
thermal, and liquid hazards. The layer that is closest to the skin, the thermal liner, consists of a face cloth quilted to batting
material. The thermal liner provides a little more than 50% of the thermal insulation (thermal protective performance – TPP)
and plays a key role in moisture management for better comfort and mobility. Moisture management is a performance
attribute exhibited by high performance thermal liners.


2)  Who is LeBron James, Usaine Bolt, and Tiger Woods?
LeBron James is one of the best basketball players in the history of the NBA. Usaine Bolt is a sprinter, the fastest man
alive, with multiple world records and Olympic gold medals. Tiger Woods is a professional golfer and one of the best
athletes to ever play the game.


3)  Love them or hate them…
The purpose of this blog is not to debate who the best NBA player is, who the best Olympian is, or the best golfer to
ever live. Love them or hate them, the competitors above are world-class athletes who perform at the top of their game
for their respective sports.


Back to the original question – What do high performance thermal liners have in common with the apparel worn by LeBron James, Usaine Bolt, and Tiger Woods? The answer is the top athletes all wear clothing with similar attributes to that of a high performance thermal liner. One attribute high performing thermal liners and athletic apparel have in common is moisture management.


What is Moisture Management?
Moisture management is a performance attribute that involves both wicking moisture away from the skin and drying quickly. Wicking moisture away from the skin is important as it improves comfort and helps the body cool down – critical to athletes and firefighters. Drying quickly is important, as dry apparel is lighter and easier to move in than wet apparel – critical to athletes and firefighters. Moisture management leads to better comfort, better mobility, less stress, and better performance…something desired by any athlete or firefighter. It is important that firefighters understand moisture management and which fibers, yarns, and fabrics perform the best in this category.


Which Fibers, Yarns, and Fabrics Produce the Best Moisture Management?
Thermal liners that exhibit the best moisture management have a few things in common:
1) They all contain DuPont™ Nomex®, DuPont™ Kevlar®, and Lenzing® FR fibers.
2) They all contain a blend of DuPont™ Kevlar® Filament and DuPont™ Nomex®/FR Lenzing® spun yarns.
3) They all contain a twill weave construction.


One thermal liner fitting this description is Glide™ thermal liner that is specified by more top metro cities than any other thermal liner. A brief list of departments wearing Glide™ include Los Angeles, Chicago, Houston, Philadelphia, Phoenix, San Diego, Seattle, Miami, San Francisco, Kansas City, Wichita, Portland, Jacksonville, Orlando, and more cities than we can mention.


A picture tells a thousand words
A picture tells a thousand words…or does it? Some textile companies will show pictures, videos, or demonstrations that include dropping water on a thermal liner and insinuating that if the water quickly disappears it must have excellent moisture management. Those who understand moisture management will know that this demonstration alone is a sales tactic designed to quickly convince the firefighter that they have a high performance thermal liner. Those who understand moisture management know the following:

1) Some thermal liners use wicking finishes that absorb a drop of water quicker than a thermal liner, like Glide™, that does not have a wicking finish. However, wicking finishes are only effective brand new and out of the box. After wash the wicking finish goes away…along with the quick absorption of water.


2) A drop of water that quickly disappears on a thermal liner does not mean it has good moisture management. The proof: drop some water on a cotton t-shirt and watch the water quickly disappear…does anyone think cotton fabric has good moisture management? Of course not.


3) It is the combination of wicking moisture away from the skin and drying quickly that dictates whether a thermal liner maintains good moisture management. The only way to know the true performance of a thermal liner is to wear it or ask local departments or departments referenced above. For sure, don’t be fooled by tricky demonstrations with tricky finishes that don’t last.


Fighting fires can be as much an athletic activity as playing basketball, sprinting, or playing football. Is moisture management
the most important characteristic of a high performance thermal liner? If not, what is the most important performance characteristic?