Understanding FR: Behind the Spiritus Mission Line
Posted by Zane Vogel on Aug 27th 2026
I’ll never forget the disappointment of receiving the first Flame Resistant (FR) clothing I was expected to wear during our deployment to Afghanistan. We all knew people who had been badly burned, and none of us wanted to experience that horror ourselves. The Army’s solution was to provide garments that were thick, stiff, itchy, smelled awful, and had equal amounts of issues with the design and patterning. But we wore them anyway; because we wanted the protection and because our command required it.
Inevitably, after a few months in the southern Afghan summer, most of our Unit started swapping the FR items out for more traditional options. It was the classic tradeoff: give up something that was designed for an event in the Most Dangerous quadrant of the risk matrix in favor of something better suited to the Most Likely quadrant, all because the protective uniform was distracting and just plain awful during daily wear. We believed that if we became heat casualties or spent the entire day fighting our clothing, we weren’t going to be able to focus on the mission and bring 100% to the fight.
To be honest, the first time we at Spiritus discussed making an FR shirt, I was incredibly hesitant. I had such a negative experience with my issued FR clothing that I didn’t want to bring another uncomfortable option to our customers and pretend that discomfort was simply the price of protection.
As we worked through the development, I was amazed at how far a little care could go. Choosing FR didn’t have to mean accepting a garment that was miserable to wear. Once again, Big Army did Big Army things and delivered the wrong items to people who eventually stopped using them, all at the taxpayers’ expense.
The material we selected for the Mission line is lightweight, soft, breathable, robust, fast drying, and inherently flame resistant. It felt closer to pajamas than any FR garment I had ever been issued. I was blown away.
So, what is FR, anyway?
Flame resistance is a material’s ability to resist ignition, limit the spread of flame, and stop burning after the ignition source is removed. It does not mean the material cannot burn, and it definitely does not mean the person wearing it is fireproof. The purpose is to keep the garment itself from becoming another source of injury.
There are two broad ways protective textiles achieve flame resistance: inherent FR fibers and durable FR treatments.
Inherent FR fabrics are made using fibers whose flame-resistant properties exist within the chemical structure of the fiber itself. Aramids (e.g. Kevlar) and modacrylics are common examples of synthetic FR fibers. When exposed to sufficient heat, these materials resist supporting combustion and form a stable char rather than continuing to burn or melting like conventional thermoplastic synthetics.
Natural fibers add another dimension to the conversation. Wool has excellent natural flame-resistant properties. It is difficult to ignite, does not melt or drip, and generally self-extinguishes once the ignition source is removed. Wool’s natural moisture and nitrogen content mean it requires more oxygen to sustain combustion than is normally available in the atmosphere, and its structure forms an insulating char when exposed to high heat.
We like wool, and I expect it may have a place in future Spiritus products. It is comfortable across a wide temperature range, handles odor well, does not melt, and has a long-standing history of being used in protective clothing.
The important part is that with inherent FR, the flame resistance is part of the fiber. It is not a coating sitting on top of the fabric, so it cannot simply be washed out. The garment can still wear out, become contaminated, or sustain enough physical damage that it should be replaced, but ordinary laundering will not remove the property that makes the fiber flame resistant.
Treated FR takes a different route. It begins with a fiber or fabric that would otherwise burn and uses durable chemistry during manufacturing to change how it reacts when exposed to a flame. Properly manufactured, treated FR, is a legitimate protective material and can meet recognized performance requirements while retaining its flame resistance through the intended life of the garment.
Unlike a basic flame-retardant surface treatment, which is an important callout. Those treatments are commonly used on products like furniture, carpet, and curtains. They are not interchangeable with professionally engineered protective fabrics simply because they sound the same. Flame retardant and flame resistant are not interchangeable, and it’s important to understand the difference when referencing tactical garments.
For the Mission Rugby Shirt and the rest of the Mission line, we believed a modacrylic and FR rayon blend was the right material for the application. This combination would provide something extremely lightweight and breathable that would manage moisture, dry quickly, remain comfortable under armor, and perform well during sustained activity in extreme environments.
The specific blend allows the fibers to perform different jobs within the same material. The modacrylic portion provides inherent flame resistance and no-melt/no-drip functioning. The FR rayon helps give the garment its softness, moisture absorption, vapor movement, and next-to-skin comfort without introducing a conventional melting synthetic fiber into the system.
*Warning: technical jargon ahead, but I have faith you can handle it.
The result of this combination is a 4.8-ounce-per-square-yard material that feels nothing like the FR garments I remembered wearing. It manages moisture, dries quickly, maintains its shape, and uses silver-ion technology to control the bacteria responsible for odor. It has been evaluated for flame resistance and no-melt/no-drip behavior using ASTM D6413, for air permeability using ASTM D737, and for colorfastness to laundering using AATCC 61. The material is Berry Amendment compliant and made entirely in the United States.
Another important callout is to clarify the difference between Flame Resistant and No-Melt/No-Drip (NMND).
Think about melting the end of some 550 cord with a lighter and touching it too soon. That melted nylon is exactly the kind of hazard NMND materials are designed to prevent. The biggest difference is that even though NMND materials can still burn, they are designed to not turn your shirt into one big, melted blob of 550 cord directly on your body. Ain’t nobody got time for that.
Under intense exposure to fire, NMND materials may reduce the injury associated with melting and dripping compared with conventional nylon, polyester, and other thermoplastic synthetics, but NMND is not the same thing as FR. Flame-resistant materials are designed to resist ignition, limit flame spread and self-extinguish after the ignition source is removed. Both have their place, and you will continue to see each in our combat apparel offerings.
The most common NMND fabric you’ll see in the tactical space is NYCO, which is a blend of nylon and cotton. This is a fantastic material that combines the strength and abrasion resistance of nylon with cotton to create a fabric that does not present the same melt-and-drip hazard as conventional synthetic performance fabrics (but keep in mind that conventional NYCO is not automatically flame resistant). It may avoid the melt-and-drip behavior of traditional synthetic materials while still igniting and continuing to burn. That is the differentiation between the two technologies.
NYCO can also be taken a step further and made flame resistant. Cotton is a cellulosic fiber, which means it can accept durable FR chemistry during the manufacturing process. That chemistry changes how the cotton reacts to heat, promoting char formation instead of allowing it to continue feeding the fire. When combined with an appropriate nylon component and properly engineered as a complete fabric, the result is FR NYCO: a material that retains the strength, abrasion resistance, and familiar feel of conventional NYCO, all while taking it from NMND to a legitimate FR system.
This is also why the entire clothing system matters. An FR outer layer worn over a conventional polyester T-shirt has not solved the problem. The layer against your skin is exactly where melting material can do the most damage, and an FR label on the garment over it does not change that. Conversely, wearing FR next to your skin creates a protective barrier beneath your tactical nylon kit.
You need to understand every layer you are wearing and know how to combine those layers appropriately for the threat.
After learning about FR materials, I went from hesitant to passionate about our push to provide a high-quality, American-made FR line of next-to-skin apparel. We wanted to protect people from a truly terrifying possibility without forcing them to sacrifice comfort and performance during the other 99% of the mission, which was the exact compromise we experienced in Afghanistan.
The bartering between protection and everyday comfort, mobility, and effectiveness is no longer necessary. You should not have to choose between protection during the worst moments and performance during every other. The right materials, patterning, and construction can deliver both, which is how products in this space should have been built all along.
That is why the Mission Line exists. As long as American warfighters step into the heat of violence, Spiritus Systems will continue to develop the best possible solutions that bring them home.
-ZV
