All fire resistant fabrics comply with 29 CFR 1910.269(1)(6)(iii). Untreated cotton and wool comply if the fabric will not ignite and continue to burn under the conditions to which the employee could be exposed. ASTM F1506-94 and 2 new ASTM provisional standards, outline the testing procedures to determine how various fabrics react in the presence of an electric arc on an instrumented mannikin or panel. The new ASTM provisional standards provide testing procedures that expose untreated and fire resistant fabrics to electric arcs. F1506-94 provides testing procedures that expose these same fabrics to a vertical flame test. Also see NFPA 70E, Part II, Ch. 2-3.3.3 for details on flash hazard analysis.

7.4.8.2 ELECTRIC ARC HAZARDS

Electric shock is a widely recognized hazard and involves current flow through or on the body. Burns from electric arcs are not as well recognized. There is no contact required and the burns can be severe if the clothing ignites or melts. The hazards to which the employee is exposed also include the clothing breaking open due to the arc pressure blast, the heat from the electric arc and subsequent secondary fires or explosions.

The extent of the employees' injury is dependent on the length of the arc gap, available fault current, duration of the arc, the distance of the employee from the arc, percentage of the body burned, the employees age, medical condition, and number of layers of the clothing system. The proper clothing system will minimize or reduce the burn injury.

7.4.8.3 TYPES OF FIRE RESISTANT FABRICS

Chemically dependent fire resistant fabrics are treated with flame retardant chemicals added to the fiber or treatments applied to the fabric. These treatments are activated by heat and produce gases that smother the flame. Typically, these fabrics have a definite life as defined by the manufacturer. This is usually defined by the number of home or commercial washings the garment is exposed.

Inherently fire resistant fabrics, by their composition, do not burn in air. The fire resistance of this fabric is not affected by washing.

¹ See Appendix D, Reference Matrix.

7.4.8.4 CLOTHING SYSTEMS

All clothing worn by affected workers should be considered part of the employees protective clothing system. This includes rainwear, cold weather wear and underclothing. Protective clothing should provide a good functional fit to increase the protection and comfort of the clothing. When required, protection can be increased by wearing single or multiple layers of flame resistant outer garments over nonmelting clothing. Sleeves and shirts should be fully buttoned and appropriate neck, head, and hand coverings provided.