Which of the following should not have wiring installed within ducts?

Installing wiring within ducts poses significant safety risks, particularly in environments where certain materials are present. When considering whether to install wiring in ducts, it is essential to avoid scenarios where there might be the presence of dust, flammable vapors, or loose stock.

Dust can accumulate on wiring and electrical components, creating a potential fire hazard. It may also interfere with the cooling of equipment, leading to overheating.

Flammable vapors significantly increase the risk of combustion. If an electrical component were to spark, it could ignite the vapors, resulting in a dangerous situation.

Loose stock can create physical obstructions and could lead to wires being damaged or severed, which could also result in short circuits or failures, posing both fire and shock hazards.

Given these considerations, it is clear that none of these conditions are appropriate environments for installing wiring, making the choice to avoid all of them the correct decision.