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EBT

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Energy Break-Open Threshold (EBT) is reported when ATPV cannot be measured due to FR fabric breakopen during testing to ASTM F 1959.

Wow - that sounds bad, doesn't? Who wants their fabrics to break open in the event of an arc flash?

Let's clarify: all flame resistant garments/fabrics that have an arc rating in either EBT or ATPV have been tested to ASTM F 1959. When flame resistant clothing or fabric is tested via test method ASTM 1959, two things can occur: the garment or fabric will break open (results recorded in EBT) or will not break open, and will remain intact while surpassing the heat threshold for a 50% probability of a 2nd degree burn, based on the Stoll curve (results recorded in ATPV). Both values, EBT and ATPV, are measuring calories per square centimeter and represents the maximum performance capability for arc-flash protection of a particular garment or fabric.

In the scientific sense - think fiber bonds, molecules, etc - knits and fleeces (sweatshirt material) are "weaker" fabrics. This doesn't mean you shouldn't buy a sweatshirt or a comfortable FR knit shirt as reliable flame resistant protection. It means that when they are tested, the fabric will not withstand the incident energy to surpass the heat threshold.

See also ATPV.