The marking shall specify the temperature class or operating temperature at a 40°C ambient temperature, or at the higher ambient temperature if the equipment
is rated and marked for an ambient temperature of greater than 40°C. For equipment
installed in a Class II, Division 1 location
, the temperature class or operating temperature shall be based on operation of the equipment
when blanketed with the maximum amount of dust that can accumulate on the equipment
. The temperature class, if provided, shall be indicated using the temperature class (T codes) shown in Table 500.8(C)
for Class I and Class II shall be marked with the maximum safe operating temperature, as determined by simultaneous exposure to the combinations of Class I and Class II conditions.
Exception: Equipment of the non-heat-producing type, such as junction boxes, conduit, and fittings, and equipment of the heat-producing type having a maximum temperature not more than 100°C shall not be required to have a marked operating temperature or temperature class.
Informational Note: More than one marked temperature class or operating temperature, for gases and vapors, dusts, and different ambient temperatures, may appear.