The words 'Inherent' is commonly used when referring to flame resistant (FR) fabrics, but very few people understand the relevance of the terms. Unfortunately, there was a section about 'inherent'vs. fireproof fabrics that was mistake, incomplete correct, and/or misleading on this topic, necessitating a review of the facts.
The word inherent was not originally a textile or FR term. Its definition varies slightly from source to source, but the common thrust is 'by its very nature, built-in, implicit,' while 'treated' is usually defined as chemical engineering to impart properties not previously present. Nature provides very few FR fibers, the most well known of which is asbestos, which is obviously not in common use in protective apparel in North America today. What is important is not how the engineering was accomplished; what matters is that the engineering was accomplished, correctly and consistently.Conversely, all fire retardant fibers in common use today for industrial protective apparel are engineered by humans, using chemistry, to be flame resistant.
Similarly, most 'treated' products begin as naturally occurring flammable substances (usually cotton or other cellulosics), so nature has already taken care of the fiber portion, and humans get involved to engineer the FR .The 'inherent' fibers tend to be synthetics, and most begin as naturally occurring flammable substances (petrochemicals), not fibers. Humans must intervene, using chemistry, to engineer the fiber and the FR properties within it.