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Back to Basics: What does “FR” Mean?

Let’s get back to basics and explore what the acronym “FR” really means.  You probably hear FR used in many different contexts, but it doesn’t always carry the same meaning.  There is “FR” clothing made of “FR” materials.  Some of those materials contain inherently “FR” fibers, while some of the fabrics require “FR” treatments to make the fabric “FR”.  So, what does “FR” mean?

FR vs FR

“FR” has two distinct meanings as it relates to protective clothing, and they’re far from interchangeable.  FR can be:

  • Fire Retardant – A chemical treatment
  • Flame Resistant – A property of a material

FR - Fire Retardant

Fire retardants, or FR treatments, are chemical finishes that are added to fabrics to make them flame resistant.  They can be made up of a variety of different chemistries that are often proprietary.  The treatments are applied to fabrics that are made of naturally flammable materials, like cotton.  Two very common fabric types with FR treatments are “FR Cotton” (i.e. 100% cotton, treated with a fire retardant), and “88/12” (i.e. a blend of 88% cotton and 13% Nylon, with the resultant fabric being treated with a fire retardant).  

A key takeaway is that a fabric is not, in itself, fire retardant.  Fabrics are treated with fire retardants to make them flame resistant.  

FR - Flame Resistant

Flame Resistance is a property of flame resistant (FR) materials.  Being categorized as flame resistant typically means that the fabric will quickly self-extinguish after a flame source is removed.  The amount of time it takes to self-extinguish is measured using the Vertical Flame Test, ASTM D6413.  Nearly all protective clothing specifications allow for up to 2-seconds of afterflame time in this test for a fabric to be considered Flame Resistant.  

How is "Inherent FR" Different?

Flame resistance doesn’t just apply to fabrics.  Some fibers themselves are also flame resistant.  If the fiber, from its initial production, is flame resistant on its own, that fiber is considered to be “inherently flame resistant”.  If a fabric is made from all inherently FR fibers, no post-treatment with fire retardant (FR) chemistry is required.  Certain types of inherently FR fibers can be blended, in certain ratios, with non-FR fibers to create a fabric that still performs well enough to be categorized as and FR fabric, without the need for FR treatments.  

Inherently FR fiber types include, but are note limited to Aramids (e.g. Nomex and Kevlar), Modacrylics (e.g. Protex),  FR Rayon (e.g. LenzingFR), and Polybenzimidazole (e.g. PBI).

It is widely recognized that the flame resistance properties of Inherent FR fibers can never be “washed out”.  But nearly all modern FR treatments are quite durable and survive multiple launderings and the fabrics typically remain flame resistant throughout the life of the garment. 

What about "AR" - Is that the same thing?

Short answer: No.  The term AR stands for Arc Rated.  The relationship between AR and FR leans on some very simple logic.  All AR fabrics are FR, but not all FR fabrics are AR.  

Flame resistance (i.e. an FR Fabric) is a prerequisite for determining an Arc Rating.  All the standards for for Arc Rated clothing require that the fabric must first be confirmed as flame resistant.  The only thing that makes a fabric AR is the fact that it has an arc rating as determined by arc flash testing.  While all AR fabrics are FR, there are many FR fabrics that are not AR.  According to OSHA, PPE must match the hazard.

Need to verify performance of an FR or AR fabric/garment?

Kinectrics ArcWear confirms FR properties of fabrics everyday in our ISO 17025-accredited testing lab in Louisville, Kentucky.  

Kinectrics ArcWear also performs arc flash testing at least one week every month at the Kinectrics High Current Laboratory in Toronto, Ontario.

Please contact us today to discuss your testing needs.

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