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FR Terminology

ANSI - The American National Standards Institute is a membership organization founded in 1918 that coordinates the development of U.S. voluntary national standards in both the private and public sectors. It is the U.S. member body to SO and IEC.


Arc flash – Is a voltage breakdown of the resistance of air resulting in an arc which can occur where there is sufficient voltage in an electrical system and a path to ground or lower voltage.


Arc rating - Are values that indicate the arc performance of a material or system of materials and are expressed in calories per centimeter squared.

ATPV- (ATPV) is a rating assigned to FRC indicating the level of protection provided. Higher fabric weights typically have higher ATPV's and provide increased protection as does the layering of flame-resistant clothing. ATPV is measured in calories per centimeter squared (cal/cm2).


ASTM - ASTM International (formerly The American Society for Testing and Materials) is a not-for-profit standardsorganization focused on developing voluntary codes and regulations for technical materials, products, systems, andservices. Established in 1898 to set standards for railroad steel, the organization also works in such areas as petroleum, medical devices, consumer products, and environmental assessment.

Breakopen - Is the formation of holes in the fabric due to arc rating testing. This deterioration of a flame resistant fabric, caused by breakopen, would allow heat or flames to pass through. This cal/cm² rating is expressed as EBT, rather than ATPV.

Char Length – A measurement of the damaged fabric after the Vertical Flame test.


EBT - Energy Break-Open Threshold (EBT) is reported when ATPV cannot be measured due to FR fabric breakopen.

Flame resistant - A material that burns slowly or is self-extinguishing after removal of an external source of ignition.

Flame retardant - Used to describe something that is hard to ignite; that does not support or convey flame.


FRC – Flame-resistant clothing.


High Visibility - Has highly reflective properties or a color that is easily discernable from any background.

HRC- Hazard Risk Category (HRC) is a rating range directly related to ATPV. There are 5 HRCs ranging from 0 to 4, with a hazard risk of 0 presenting the least risk and a hazard risk of 4 being the greatest risk.

       Hazard Risk Category Rating (HRC)

                1       4 or more ATPV

                2       8 or more ATPV

                3       25 or more ATPV

                4       40 or more ATP



HTP – The Heat Transfer Performance of a fabric, or the amount of heat it takes to pass through the fabric to cause second-degree burns based on the skin burn curve. NFPA 2112 requires a fabric to have a minimum of 6 cal/cm² when tested with a spacer and 3 cal/cm² in contact.


Inherent flame resistance - As applied to textiles, it is the flame resistance derived from the properties of the fiber from which the textile is made.

Manikin Test/Body Burn– A simulated flash fire test using an instrumented manikin to calculate the estimated percentage of second and third degree body burn after three seconds of exposure. NFPA 2112 requires the percentage to be below 50%.

PPE-  (personal protective equipment) Personal protective equipment is specialized protective gear, not 'standard issue' clothing or equipment, worn by an employee for protection against a hazard.

TPP – The Thermal Protective Performance of a fabric. It is the amount of heat it takes to pass through the fabric and cause a second-degree burn. CGSB 155.20 requires a fabric to have a minimum of 6 cal/cm² when tested with a spacer.


Vertical Flame Test – A basic test that determines whether or not a fabric is FR by measuring how much of the fabric is consumed after 12 seconds of flame exposure.


Visible Light Transmission  - Is the amount of light viewable through a faceshield or goggle. As a faceshield or goggle achieves higher arc ratings, the amount of visible light transmitted is reduced.