220-1101 Question 200
Single answerPlenum-ratedA technician is installing new Ethernet cable for wireless access points in an office building. The cable must run through the space above the suspended ceiling, and the building inspector confirms that this area is used for air circulation by the HVAC system. To pass inspection and meet safety requirements, which type of cable should the technician install?
- A
Plenum-rated cable (CMP)
- B
PVC-jacketed riser cable (CMR)
- C
Direct-burial shielded cable
- D
Standard patch cable with RJ-45 connectors preinstalled
Show answer and explanation
Correct answer: A
Explanation
When network cable is installed in a plenum space, the primary concern is fire safety in an air-distribution area. Plenum-rated cable (CMP) uses jacket materials that limit smoke generation and toxic fumes during combustion. This is why it is required by code in spaces used to circulate air for HVAC systems, such as many drop ceilings and raised floors. Riser-rated cable (CMR) is for vertical shafts between floors and is not a substitute in plenum spaces. Direct-burial cable is for underground outdoor use, and standard patch cables are not selected based on plenum compliance. In practice, technicians should verify local building and fire code requirements, which commonly align with National Electrical Code (NEC) guidance for communications cabling in plenum environments.
- A. Correct.
Correct. Plenum-rated cable, commonly marked CMP, is designed for use in plenum spaces such as air-handling areas above dropped ceilings or below raised floors. Its jacket materials produce less smoke and fewer toxic fumes if exposed to fire, which is why building codes typically require it in these spaces.
- B. Incorrect.
Incorrect. Riser-rated cable (CMR) is intended for vertical runs between floors in non-plenum spaces. Although it has fire-resistance characteristics appropriate for riser shafts, it does not meet the stricter smoke and toxicity requirements for air-handling plenum spaces.
- C. Incorrect.
Incorrect. Direct-burial cable is designed for outdoor installation underground and includes protection against moisture and environmental exposure. That rating does not make it suitable for indoor plenum areas, where low-smoke, fire-safety requirements are the key concern.
- D. Incorrect.
Incorrect. A standard patch cable may be convenient for short device connections, but its preinstalled connectors and typical jacket type do not address plenum safety requirements. The issue in this scenario is the cable jacket rating for an air-handling space, not whether the cable is terminated.