![]() Stoll showed that regardless of the mode of application of heat, the temperature rise and, therefore, the tolerance time are related to heat absorbed by the skin. Stoll and associates performed experimental research to determine the time it takes for second-degree burn damage to occur for a given heat flux exposure. We will focus on second-degree burn as this is the kind of burn used to determine the arc-flash boundary in engineering arc-flash analysis studies.Īlice Stoll pursued the basic concept that burn injury is ultimately related to skin tissue temperature elevation for a sufficient time. A variety of studies on thermal effects have been performed and thermal thresholds identified for different degree burns. Some tests were also performed on human volunteers on the fronts of the thorax and forearms. Tests were performed on a large number of anaesthetized pigs and rats exposed directly to fire. To name the few, are the works done by Alice M. In order to protect people from fires, atomic bomb blasts and other thermal threats, it was first necessary to understand the effects of thermal trauma on the skin. Much of the research which led to equations to predict skin burns was started during or immediately after World War II. The important point to note here is that threshold incident energy level for a second-degree burn or onset to second-degree burn energy on a bare skin is considered constant value equal to 1.2 cal/cm 2( 5.0 J/cm 2) in IEEE P 1584 standard.įlash Fire Burn Experimentations and Observations 2IEEE 1584 Guide states that “the incident energy that will cause a just curable burn or a second-degree burn is 1.2 cal/cm 2( 5.0 J/cm 2).” 1To better understand these units, IEEE P 1584 refers to an example of a butane lighter: “If a butane lighter is held 1 cm away from a person’s finger for one second and the finger is in the blue flame, a square centimeter area of the finger will be exposed to about 5.0 J/cm 2or 1.2 cal/cm 2.” However, IEEE P 1584 equations 5.8 and 5.9 for determining the arc-flash boundary can also be solved with other incident energy levels as well, such as the rating of proposed personal protective equipment (PPE). 1Also, NFPA 70E 2states that “a second-degree burn is possible by an exposure of unprotected skin to an electric arc flash above the incident energy level of 1.2 cal/cm 2( 5.0 J/cm 2)” and assumes 1.2 cal/cm 2as a threshold incident energy level for a second-degree burn for systems 50 volts and greater. The incident energy of 1.2 cal/cm 2( 5.0 J/cm2) for bare skinwas selected in solving equation for the arc-flash boundary in IEEE P 1584. ![]() The incident energy to which the worker’s face and chest could be exposed at working distance during an electrical arc event was selected as a measure for determining hazard risk category and calculating arc-flash protection boundary. The IEEE P 1584 was developed by having incident energy testing performed based on methodology described in the ASTM F1959-99 standard. Use of Incident Energy as a Measure of Burn Severity in Arc-Flash Boundary Calculations ![]() The formulas are based on incident energy testing performed and calculations conducted for a selected range of prospective fault currents, system voltages, physical configurations, etc. Among others, the IEEE Standard P 1584 Guide for Performing Arc-Flash Hazard Calculations1 and formulas provided in Annex D of NFPA 70E2 and CSA Z462 Workplace Electrical Safety Standard are the most often utilized in the industry to perform arc-flash hazard analysis. ![]() During the last two decades different formulas have been proposed to calculate incident energy at an assumed working distance, and the arc-flash boundary in order to determine arc-rated personal protective equipment for qualified electrical workers. Our interest in determining accurate onset to second-degree burn energy and its significance in computing the arc-flash boundary is focused on the prevention of injury to the skin of a human who might be exposed to an arc flash. ![]()
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