ATPV stands for Arc Thermal Performance Value, and it’s measured in calories per square
centimeter (cal/cm²) of fabric. Let’s say that a certain fabric has an ATPV rating of 8 cal/cm². That
means that this fabric can protect the wearer against 8 calories of energy (flame, heat) per square
centimeter before there is a 50% chance that the fabric will burn through and the wearer will suffer
a second-degree burn. All testing of fabrics to determine their respective arc ratings is done at one
independent laboratory, Kinectrics of Toronto, Canada.