April 11, 2019 / Derek Sang

Treated vs. Inherent Flame-Resistance

Sponsored by Bulwark

There’s a lot of confusion about the terms “treated” and “inherent” flame-resistant clothing (FR). What’s the difference? And, more importantly, does one offer better protection than the other?

In short, the answer is no. But to understand why, we must start by understanding what these terms mean and why they were applied to FR fabric in the first place.

Definition and Engineering

“Inherent” FR refers to a fabric that has FR properties—the fabric’s ability to self-extinguish when the ignition source is removed—by its very nature. In other words, inherent FR refers to a fabric that is FR without any additional finishing. “Treated” FR, on the other hand, refers to a fabric that has been engineered with flame-retardant chemistry to have FR properties that were not present prior to the treatment.

There are three levels at which FR properties can be achieved:

  • The molecular level—synthetic derivatives are engineered at the molecular level to be FR. Examples include Nomex, Kermel, Twaron, Kevlar, among others.
  • The fiber level—flame-retardant chemicals are added to the process prior to the fiber being extruded. FR modacrylics and FR rayons are two examples of fabrics that are FR at the fiber level.
  • The fabric level—FR properties are permanently imparted into flammable fabrics through a combination of chemical and mechanical processes. Examples include FR cotton and 88/12 (the numbers refer to the composition of the fabric, which is 88 percent cotton and 12 percent nylon).


When the terms inherent and treated were adopted by the FR world over 30 years ago, they reflected the durability of flame-resistant technology at that time. Back then, the intent was to imply that “inherent” was superior to “treated.” Why? Because at one time, it was true. Cotton and other cellulosic materials are naturally flammable, so they do have to undergo a chemical process, or “treatment,” to impart FR properties. And these early “treated” garments did lose their FR properties over time and after repeated washings. Treated fabrics, prior to 1987, could not compete with aramids (a kind of heat-resistant fiber) as a durable FR alternative.


Over the past 30 years, however, we’ve made dramatic advancements in FR technology that have blurred the lines between these two terms. “Inherent” and “treated” have become so common and so misused that the terms now create more confusion than clarity. Most popular FR fabrics today are blends of several different fibers, and this has created confusion on where and when to apply the current labels. Because “inherent” and “treated” refer to single fiber types, they fail to accurately represent today’s complex blends—which sometimes combine all three engineering levels. For example, what should we call a fabric that is 35 percent aramid (engineered at the molecular level) and 65 percent FR cotton (engineered at the fiber level)? When a fabric is a combination of both inherent and treated FR fabrics, and with no rules in place about how to apply the terms, they become more confusing than helpful.

FR to Count On

FR technology has come a long way. The fabrics in use today are far superior to those of just a generation previous, and the terms we use to discuss them must make the same evolution. The bottom line is, when it comes to selecting FR fabrics, the most important considerations should always be protection, comfort, and durability. No matter which fabric you select, be sure that you can count on the FR properties to last, wash after wash. Bulwark offers an FR guarantee for the lifetime of the garment, on all of our products, to ensure your safety program does what it’s supposed to do: keep you and your workers safe.

To explore Bulwark’s FR fabric selection and learn more about its lifetime guarantee, get in contact with a sales rep today.

Derek Sang

Derek Sang has been involved with the flame-resistant clothing industry in a variety of roles from the service, manufacturing, and garment sides of the business for over 20 years. Along with being a recognized subject matter expert, Derek is also a Qualified Safety Sales Professional (QSSP); Certified Environmental, Health, and Safety Professional (IASHEP); Certified Safety, Health, and Environmental Technician (IASHEP); and recently a qualified trainer for low voltage based on the NFPA 70E standard. 


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