NFPA 70E Table 130.7(C)(11) recommends typical protective clothing systems and characteristics including the degree of protection for various clothing. The protective clothing selected for the corresponding hazard/risk category number shall have an arc rating of at least the value listed in the last column of Table 130.7(C)(11). The arc rating for a particular clothing system can be obtained from the Flame-Resistant (FR) clothing manufacturer.
NFPA 70E Table 130.7(C)(11) provides general information which assists a worker to understand the process for selecting clothing based on a hazard/risk category designation. The table describes the protective nature of clothing that meets a specific hazard/risk category. The table is intended for use in conjunction with Table 130.7(C)(9)(a) but it can be used with other methods of determining the necessary protective clothing.
When FR clothing meeting the requirements of ASTM F 1959, Standard Test Method for Determining the Arc Rating of Face Protective Products, 2002, is exposed to an electrical arc to establish its rating, the rating is the failure mode in which the material chars and breaks open. Charring causes the fibers of the material to close the mesh in the material weave. The charred fabric could break open and expose the material (or skin) underneath. The arc rating of FR clothing is either the arc-thermal performance value (ATPVÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬ÂASTM F 1959) or the energy level (ASTM F 1959) that caused break open to occur when the fabric was tested.
|Hazard/Risk Category||Typical Protective Clothing Systems Clothing Description
(Typical number of clothing layers is given in parentheses)
|Required Minimum Arc Rating of PPE
|0||Non-melting, flammable materials (i.e., untreated
cotton, wool, rayon, or silk, or blends of these
materials) with a fabric weight at least 4.5 oz/yd2 (1)
|1||FR shirt and FR pants or FR coverall (1)||16.74 (4)|
|2||Cotton underwear‚ conventional short sleeve and brief/shorts, plus FR shirt and FR pants (1 or 2)||33.47 (8)|
|3||Cotton underwear plus FR shirt and FR pants plus FR coverall, or cotton underwear plus two FR coveralls
(2 or 3)
|4||Cotton underwear plus FR shirt and FR pants plus multi-layer flash suit (3 or more)||167.36 (40)|
Source: NFPA 70E 2004, Handbook for Electrical Safety in the Workplace 2004