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  • OSHA CFR 1910.269 "...prohibits clothing, that when. exposed to electrical arcs, could increase the extent of injury that would be sustained by the employee." (I)(6)(iii)
  • An employee must wear flame-resistant (FR) clothing to work around energized parts.
  • To evaluate FR clothing materials in order to measure the heat transferred through the fabric, two values are calculated: arc-thermal performance value (ATPV) and heat attenuation factor (HAF).
  • ATPV is the minimum energy causing the predicted onset of seconddegree burns.
  • HAF is the percentage of total energy of the arc that the fabric prevents from passing through.
  • Heavier or layers of FR fabrics give higher ATP values.
  • Layering of non-FR clothing under an outer shell of FR fabric can give a false sense of security. If the outer layer should break open, the inner clothing could ignite.
  • OSHA requires that each employer must assess the potential hazards in the work environment and determine the appropriate clothing materials using ASTM PS57-97.
  • Always do a hazard assessment. You will need to know electrical system voltage, fault current available, number of phases, arc time duration, estimated arc gap, minimum distance from the arc, and configuration of the arc.
  • As you move further away from an electrical arc the heat is reduced according to the inverse square rule. Moving back two feet from the arc would reduce exposure to 1/4, three feet to 1/9, four feet to 1/16, etc. Based on distance and other arc-related factors, gold and clear U/V face shields can still afford a low degree of protection.