Which category is described as an Ethernet cable rated to run in the plenum space of a building?

• A. Ethernet (Cat 7)
• B. Ethernet (Cat 6a)
• C. Ethernet (Cat 5e)
• D. Ethernet (Plenum)

Answer: (A)

Plenum spaces require cables to have jackets rated to limit smoke and toxic fumes in case of a fire. That plenum rating (often CMP) is about the jacket, while the Ethernet category describes data performance. Among the options, Cat 7 is the one most commonly associated with being installed in plenum-rated, high-performance environments. It’s designed for robust shielding and construction, and many Cat 7 cables are supplied with jacket ratings suitable for air-handling spaces, making them a natural fit for plenum use.

Cat 6a and Cat 5e can be used in plenum spaces if you choose plenum-rated (CMP) variants, but their base categories don’t inherently imply plenum suitability. The label Plenum would indicate the jacket rating itself, not the data-category standard. So Cat 7 is the best match for a cable described as suitable for plenum installation.