Energy Break-Open Threshold

Last updated: March 27, 2024

What Does Energy Break-Open Threshold Mean?

The energy break-open threshold (EBT) refers to the highest amount of electrical energy that a given material can withstand before breaking open (tearing or cracking).

It is a measurement of a material’s ability to protect workers against arc flashes and other discharges of energy, and it is defined as the point at which the material exhibits a 50% probability of break-open.

Safeopedia Explains Energy Break-Open Threshold

It is important to note that a break-open is a break in the material of at least 1.6 cm2, or 0.5 in2. For the purpose of safety, this minimum amount of break-open refers to the point at which the worker wearing the broken-open material faces a 50% probability of experiencing a second-degree burn due to exposure to the incident energy.

The energy break-open threshold is one of two criteria used to determine the arc rating of a piece of clothing or other wearable material used as personal protective equipment (PPE) against arc flashes and other forms of incident energy. The other criteria is the arc thermal performance value (ATPV), which is the point at which a material that has not yet experienced break-open transmits enough heat that the wearer has a 50% chance of receiving a second-degree burn. Both the EBT and ATPV of a given material or garment are measured with a single test, and the lowest value is used to determine the material’s arc rating.

The most common testing standards used to determine EBT and ATPV are ASTM F1959 and IEC/EN 61482-1-1. Both standards use virtually identical tests to identify a material’s arc rating. As the United States and many other jurisdictions require the use of arc-rated PPE in workplaces, these testing standards have legal weight in determining whether a given garment provides sufficient protection to workers who are exposed to an electrical hazard.

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