Plenum cables in the United States typically come in which wire sizes?

• A. 18 and 20 gauge.
• B. 22 and 24.
• C. 12 and 14 gauge.
• D. 16 and 20 gauge.

Answer: (B)

Plenum cables are designed for use in air-handling spaces and must meet fire and smoke standards. For low-voltage alarm work, the wires are typically thinner because they need to be flexible and fit through tight routes in ceilings and ducts. In practice, the standard sizes you’ll see for plenum-rated alarm/data cables are 22 AWG and 24 AWG. These gauges provide enough signaling capacity for sensors and control circuits while staying easy to route. Thicker gauges like 18/20, 12/14, or 16/20 are used for higher-power electrical wiring and aren’t the typical plenum-rated choices for low-voltage alarm cabling, which is why the 22 and 24 gauge pairing is the correct, common answer.