What type of cable should be used for installations in ducts for environmental air?

For installations in ducts designated for environmental air, CL2P or CL3P cables are appropriate choices. These cables are specifically designed to minimize the risk of fire propagation and smoke development in areas where they may be exposed to air circulation, such as in environmental air handling spaces.

CL2P cable is rated for general-purpose wiring in residential and commercial environments, while CL3P cable has a higher fire-resistance rating, allowing it to be used in more demanding applications such as wiring for audio and video systems where performance is critical. The 'P' designation indicates that they have been tested for low smoke production and flame spread, making them suitable for installation in spaces where fire safety is paramount.

Using CL1P, on the other hand, would be inappropriate as it does not have the same fire ratings needed for installation in environmental air ducts. CL4P is typically used for high-performance applications and is not applicable in this context of environmental air handling spaces. Hence, CL2P or CL3P cables are the correct choices for ensuring compliance with fire safety regulations while providing effective low-voltage communication system installations in ducts.