In Class III locations, switches, circuit breakers, motor controllers, and fuses, including pushbuttons, relays, and similar devices, shall be provided with _____.
a) Class I enclosures
b) general duty enclosures
c) dusttight enclosures
d) seals at each enclosure
See answer and applicable Code reference
The correct answer is: c) dusttight enclosures
Article 503 covers the requirements for equipment installed in a Class III location. As noted in Part III, Sec. 503.115, "Switches, circuit breakers, motor controllers, and fuses, including pushbuttons, relays, and similar devices, shall be provided with dusttight enclosures."