Document YdLp9MJOnJG7mbvpen7RgV7O

TABLE 500-2(b) IDENTIFICATION NUMBERS Maximum Temperature Degrees C Degrees F 450 842 300 572 280 536 260 500 230 446 215 419 200 392 180 356 165 329 160 320 135 275 120 248 100 212 85 185 Identification Number T1 T2 T2A T2B T2C T2D T3 T3A T3B T3C T4 T4A T5 T6 (c) Temperature. The temperature.marking specified in (b) above shall not exceed the ignition temperature of the specific gas or vapor to be encountered For infor mation legardmg ignition temperatures see NFPA 325M, Fire Hazaid Pioperties of Flammable Liquids, Cases, Volatile Solids--1969 Formerly the temperature limit of each Croup was assumed to be the lowest ignition tem perature of any material in the Group, i e , 280 C for Croup D, 180 C for Group C To avoid revising this hmit as new gases are added (see hexane in Croup D and acetaldehyde m Croup C) temperature will be specified in future markings The ignition temperature for which equipment was approved prior to this requirement may be assumed to be as follows Croup A 280 C( 536 F) Croup B 280 C (536 F) Croup C 180 C (356 F) Croup D 280 C (536 F) 500-3. Specific Occupancies See Articles 510 through 517 foi lules applying to garages, aircraft hangars, gasoline dispensing and service stations, bulk storage plants, finishing processes, and flammable anesthetics 500--4. Class I Locations. Class I locations are those in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitible mixtures Class I locations shall include the following (a) Class I, Division I Locations (1) in which hazardousconcentrationsof flammable gases or vapors exist continuously, intermittently, or periodically under normal op erating conditions, (2) in which hazardous concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leak age, or (3) in which breakdown or faulty operation of equipment or processes which might release hazardous concentrations of flammable gases or vapors, might also cause simultaneous failure of electrical equipment (Fic 41-6 continues on next page ) 1271