Wiring in Hazardous (Classified) Locations

Electrical wiring in hazardous (classified) locations is significantly more restrictive than wiring in general unclassified locations. Good design ingenuity for systems in these environments is to locate as much of the electrical wiring and equipment outside the classified location. The basic approach of addressing the hazardous (classified) location is to remove one or more components of the fire triangle—oxygen, fuel and an ignition source—to reduce the possibility of an explosion. Electrical installations present significant ignition sources for these environments.

1. The unique hazards associated with explosives, pyrotechnics and blasting agents are not addressed in the NEC.

Correct Answer: True

2. A ______ location is where flammable gases, flammable liquid-produced vapors or combustible liquid-produced vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Correct Answer: Class I

3. ______ locations are those that are hazardous because of the presence of combustible dust.

Correct Answer: Class II

4. Suitability of identified equipment shall be determined by which of the following?

Correct Answer: Any of the above

5. Generally, NPT-threaded entries into explosion-proof equipment shall be made up wrench tight with at least ______ threads fully engaged.

Correct Answer: All

6. Wiring methods for intrinsically safe systems installed in a hazardous (classified) location are all required to be suitable for Class I, Division 1 locations.

Correct Answer: False

7. In Class II, Division 1 locations, all utilization equipment shall be ______ for the location.

Correct Answer: Identified

8. ______ locations are hazardous due to the presence of easily ignitable fibers or because materials producing combustible flyings are handled, manufactured or used nearby, but which such fibers/flyings are not likely to be suspended in the air in quantities sufficient to produce ignitable mixtures?

Correct Answer: Class III

9. Conduit sealing fittings installed in Class I, divisions 1 and 2 locations are required to be listed.

Correct Answer: True

10. Which of the following protection techniques is not permitted to be used in a Class I, Division 1 or 2 location?

Correct Answer: Dust ignition-proof

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