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The Arc Thermal Performance Value (ATPV) is an indicator that measures the protective ability of arc resistant fabrics, used to evaluate the ability of fabrics to protect the human body from burns in arc flash accidents. ATPV value in calories per square centimeter (cal/cm ²） As a unit, it represents the arc accident energy that the fabric can block under a certain probability, in order to avoid secondary or higher burns on the human body.

Specifically, ATPV refers to a second degree burn based on Stoll curve predicted by sufficient heat transfer through the sample with a 50% probability Arc Rating. n - The performance of the material when exposed to an arc, with arc rating in Cal/cm2 and derived from the ATPV value or EB750 (hole formation below the ATPV value) arc thermal protection value (ATPV). Based on the Stoll curve, the probability of the sample transmitting heat causing a second degree burn in the body model is 50%. At this time, the energy value acting on the fabric or material initially generates the hole energy (EB750), and the sample transmitting heat can cause damage to the sample, This probability is 50% of the energy applied to the fabric or material. When the area of the hole is not less than 1.6 cm2 (0.5 cm2) or 2.5cm (1.0 cm2), the sample can be considered damaged. If the flame retardant fabric material is multi-layer, all layers must meet the definition of damage. In multi-layer samples, if certain layers are flammable, damage occurs when these layers are exposed. Heat Attenuation Factor, HAF. n - The percentage of energy blocked by the material in an arc experiment. Stoll curve. n-2 degree skin burn model prediction, commonly known as Stoll reaction. SCD (Stoll Curve Diversity): The average thermal energy value must be compared with the Stoll curve each time. If the experimental energy value exceeds the Stoll reaction value, secondary burns occur (positive SCD). If the experimental energy value is lower than the Stoll curve, no secondary burns occur (negative SCD).