What type of cable is NOT generally used in plenum spaces?

Plenum spaces are areas within buildings that are used for air circulation, typically for heating and air conditioning systems. Because of the potential for fire and the need for safety regulations in these areas, the type of cabling installed must maintain certain fire resistance standards.

The correct answer specifies CMP, or Communications Multipurpose Plenum cable. This type of cable is designed specifically to meet the stringent fire safety regulations required for use in plenum spaces, as it has a low smoke and flame rating. In contrast, other cable types like CM (Communications Multipurpose cable), CMG (Communications Multipurpose General cable), and CMR (Communications Multipurpose riser cable) do not have the fire-resistant properties required for plenum use. CM, CMG, and CMR cables are generally less restrictive in their fire resistance ratings, making them unsuitable for environments where they could contribute to the spread of fire or noxious fumes.

In summary, CMP cable is the correct type that is acceptable for plenum spaces due to its compliance with specific fire safety standards, while the other types do not meet those requirements.