NEC Special Occupancies & Hazardous Locations 4

Question 1

Under the NEC zone system, which zone describes a location where ignitable gas concentrations are present continuously or for long periods?

Accepted Answer

Zone 0

Answer

Zone 0 covers ignitable concentrations of flammable gases or vapors present continuously or for long periods (Article 505).

Question 2

In a Class I, Division 1 location, a conduit seal for an enclosure containing arcing devices must be located no more than what distance from the enclosure?

Accepted Answer

18 in. (450 mm)

Answer

NEC 501.15(A)(1) requires the seal within 18 in. (450 mm) of the enclosure.

Question 3

Threaded rigid metal conduit joints in Class I, Division 1 locations must be made up wrenchtight with at least how many fully engaged threads?

Accepted Answer

Five

Answer

NEC 500.8(E) requires NPT threaded entries and conduit to have at least five full threads fully engaged.

Question 4

Which Class II group covers atmospheres containing combustible metal dusts such as aluminum or magnesium?

Accepted Answer

Group E

Answer

Group E is assigned to combustible metal dusts in Class II locations.

Question 5

A cotton gin where easily ignitible fibers are handled would most likely be classified as which class?

Accepted Answer

Class III

Answer

Class III locations involve ignitible fibers or flyings, such as those in textile mills and cotton gins.

NEC Practice Test

NEC Practice Test

NEC Special Occupancies & Hazardous Locations 4