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.
Created by: Michael Johnston
1. The unique hazards associated with explosives, pyrotechnics and blasting agents are not addressed in the NEC.
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.
A. Class I
B. Class II
C. Class III
D. Zone I
3. ______ locations are those that are hazardous because of the presence of combustible dust.
D. Zone 0
4. Suitability of identified equipment shall be determined by which of the following?
A. Equipment listing or labeling
B. Evidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluation
C. Evidence acceptable to the authority having jurisdiction, such as a manufacturer’s self-evaluation or an owner’s engineering judgment
D. 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.
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.
7. In Class II, Division 1 locations, all utilization equipment shall be ______ for the location.
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?
9. Conduit sealing fittings installed in Class I, divisions 1 and 2 locations are required to be listed.
10. Which of the following protection techniques is not permitted to be used in a Class I, Division 1 or 2 location?
A. Explosion-proof equipment
B. Intrinsic safety
C. Hermetically sealed
D. Dust ignition-proof