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Special Occupancies Flashcards

7 cards from real NEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. In a Class I, Division 1 location, a conduit seal entering an explosionproof enclosure that contains arcing devices must be installed within what distance of the enclosure?

    Answer: 18 inches

    NEC 501.15(A)(1) requires the seal fitting to be within 18 in. of the enclosure.

  2. Which hazardous material defines a Class II location?

    Answer: Combustible dust

    Class II locations are hazardous because of combustible dust (NEC 500.5(C)).

  3. A textile mill where cotton lint is handled but not likely to be suspended in the air in ignitible quantities is classified as what?

    Answer: Class III

    Ignitible fibers and flyings make a location Class III (NEC 500.5(D)).

  4. In the Zone classification system, which zone has ignitible concentrations of flammable gases or vapors present continuously or for long periods?

    Answer: Zone 0

    NEC 505.5(B)(1) defines Zone 0 as continuous or long-term presence of ignitible concentrations.

  5. Threaded rigid metal conduit connections in Class I, Division 1 locations must have at least how many fully engaged threads?

    Answer: 5 threads

    NEC 500.8(E) requires at least five full threads fully engaged for NPT threaded entries.

  6. In a major repair garage where vehicles using gasoline are serviced, the floor area up to what height is typically classified as Class I, Division 2?

    Answer: 18 inches

    NEC 511.3 classifies the area up to 18 in. above the floor as Class I, Division 2 unless ventilation exceptions apply.

  7. In an aircraft hangar, a pit or depression below the hangar floor is classified as what?

    Answer: Class I, Division 1

    NEC 513.3(A) classifies pits and depressions below the hangar floor as Class I, Division 1.