What is the proper marking for class 2 wires used in environmental air spaces?

The proper marking for class 2 wires used in environmental air spaces is CL2P. This designation indicates that the cable is suitable for installation in spaces such as ceilings and walls that are not used for air handling, but still allow for unrestricted airflow. The "P" stands for "plenum," which signifies that the wire is rated for use in plenum areas, where it could potentially carry air used for heating, ventilation, and air conditioning. This is critical for ensuring safety and compliance with building codes, as other types of wires may not be designed to withstand the environmental risks present in such spaces.

In this context, other markings represent different characteristics: CL2E is typically used for external installations, CL2R indicates that the wire is rated for riser applications (vertical spaces between floors), and CL2X does not have standard interpretations related to environmental air spaces. Hence, CL2P is the correct choice for wiring in plenum spaces.