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Electrician Red Seal · Question

Which of the following wiring methods is NOT permitted for use in a building space used as an air plenum in a commercial building?

CEC Rule 12-010 restricts the types of wiring in air plenums to prevent the spread of fire and smoke. NMD90 (Romex) has a combustible PVC jacket and is explicit

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Question: Which of the following wiring methods is NOT permitted for use in a building space used as an air plenum in a commercial building?

Answer options:

  • Armoured cable (AC90) with an overall non-metallic jacket
  • Mineral-insulated cable (MI) ✅ Non-metallic sheathed cable (NMD90)
  • All-metal electrical metallic tubing (EMT)

Correct answer: Non-metallic sheathed cable (NMD90)

Explanation: CEC Rule 12-010 restricts the types of wiring in air plenums to prevent the spread of fire and smoke. NMD90 (Romex) has a combustible PVC jacket and is explicitly not permitted in plenums. MI, armoured cable, and metallic conduits are generally acceptable.

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