Arc thermal performance value (ATPV) is a measurement of a material’s ability to protect its wearer from injury due to exposure to an arc flash.
Specifically, the ATPV of a fabric refers to the amount of incident energy necessary for there to be a 50% probability that an individual wearing the material would suffer a second-degree burn if exposed to an arc flash.
The ATPV is one of the two values used to determine the arc rating of a piece of personal protective equipment (PPE). The other value is energy break-open threshold (EBT), which measures the likelihood that the material will break open (crack or tear) during an arc flash.
The ATPV and EBT of a fabric must be tested as part of its arc-rating process. The lower value of the two (the ATPV or EBT) is used as the arc rating of the PPE under consideration, as this value reflects the point at which the clothing’s protective capacity is likely to fail.
To ensure that PPE meets an employer’s legal requirement to provide employees with appropriate PPE in situations requiring arc-rated PPE, the PPE used must have been tested in compliance with standards put forth by either ASTM International or the International Electrotechnical Commission (IEC). ASTM standards are used to test PPE for use in the United States, while IEC standards are used for the same purpose in Europe. The above standards organizations describe how fabric must be tested to determine its ATPV according to ASTM F1959 and IEC 61482-1, respectively. A fabric’s energy break-open threshold is determined using the same test and standard.
Arc-rated clothing that complies with ASTM or IEC standards may not show the ATPV if it is higher than the EBT value. ATPV and EBT are held to be equally protective to workers.
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