For Optical fiber circuits, only ________ cables may be installed in plenums.

For Optical fiber circuits, only ________ cables may be installed in plenums.

• A. nonplenum-rated
• B. plenum-rated
• C. armored
• D. unrated

Answer: (B)

Cables installed in plenums must be plenum-rated because these air‑handling spaces require materials that limit flame spread and minimize smoke and toxic gas production in a fire. Plenum-rated fiber optic cables are tested to meet strict low-smoke, flame-retardant standards (often labeled as FPLP for fiber optic cables). This safety requirement protects occupants and allows safer operation of HVAC systems during an incident. Nonplenum-rated or unrated cables do not meet these standards and thus aren’t permitted in plenums, while armored status is about physical protection and doesn’t by itself guarantee the necessary fire/smoke performance.

Cables installed in plenums must be plenum-rated because these air‑handling spaces require materials that limit flame spread and minimize smoke and toxic gas production in a fire. Plenum-rated fiber optic cables are tested to meet strict low-smoke, flame-retardant standards (often labeled as FPLP for fiber optic cables). This safety requirement protects occupants and allows safer operation of HVAC systems during an incident. Nonplenum-rated or unrated cables do not meet these standards and thus aren’t permitted in plenums, while armored status is about physical protection and doesn’t by itself guarantee the necessary fire/smoke performance.