Materials and garments tested for IEC 61482-2 have an evaluated protection against the extreme 
heat that develops in an arc accident. The standard sets the limit of protection to avoid the second degree’s burn and you use the Stoll curve* as the basis for the evaluation. 
 
The protection lies in the flame retardant properties of the garment and at what level the material 
takes up the heat energy discharged at an arc (this is stated in cal/cm²). The higher the ability of the material or material combination to absorb the energy, the higher the protective 
function of the garment. Other hazards of an electric arc, which the standard does not include, are molten metal splashes, pressure waves, electric shocks and hazardous gases created when a fabric is vaporized.  
A layer-on-layer system of arc certified garments gives the wearer increased protection in case of an accident. In addition to the fact that each layer itself offers protection, it is primarily the air gap between each layer that constitutes the main barrier to the thermal energy. Blaklader recommends a three-layer concept with outer bearing, intermediate bearing and closest to the body, a flame-retarded support should be worn to maximize protection against heat and 
reduce the risk of burns. 
 
It is not possible to theoretically calculate the expected level of protection offered by a garment concept, but each unique material combination must be tested to get a relevant value. This is 
because even if you know the performance of each individual material, you cannot predict the effect and air gap between the layers will have. It is crucial how smooth, uneven, compliant or 
rigid, respectively, the materials are and how they work together. 
 
*) Stoll curve; The relationship between thermal energy and 
time that is the limit of second degree burn. 
 
IEC 61482-1-1 (test method) 
 
Open arc test: in this test, fabrics and garments are exposed to an open electric arc. Each fabric or 
combination of fabrics is given a value expressed as cal/cm² (calorific value). This value is the maximum incident thermal energy to which a fabric can be exposed and still provide protection against second degree burn injury. 
ATPV-Value (Arc Thermal Performance Value) indicates the amount of energy (cal/cm²) to which the material/garment can be exposed and still provide a 50% protection against the second degree’s burn. 
 
EBT50-Value (Energy Break Open Threshold) indicates the amount of energy (cal/cm²) to which the material/garment may be exposed before a 50% risk of hole formation occurs. The hole in the material/garment must not exceed 1.6 cm². 
 
ELIM-value (Incident Energy limit). As a complement to the ATPV and EBT value, an add-on for the Open Arc test is about a level for the Incident Energy Limit, called ELIM. ELIM is the upper 
limit of thermal energy a material / garment can be exposed without risking the second degree of burn for the wearer or hole formation in the material. For ATPV and EBT, there is always a (50%) risk that the second degree’s burn or hole may occur. 
 
 
IEC 61482-1-2 (test method) 
 
Box test: in this test, fabrics and garments are exposed to an electric arc confined in a box at a specific value. The arc current is 400 V and the duration is 500 ms. There are two classes for the test. The test gives a pass or fail result. Combinations of different garments or lined garments 
are often required to pass the box test Class 2. 

Reference to NFPA 70E 
 
HRC categories; Hazard Risk Category derived from the US Standard of Electrical Safety NFPA 70E. Sometimes this categorization is also used for risk assessment in Europe. 
 
HRC 1: 4-8 cal/cm²  
HRC 2: 8-25 cal/cm²  
HRC 3: 25-40 cal/cm² 
HRC 4: >40 cal/cm² 
 
The HRC categories are now referred to as Arc Flash PPE Category.