Plenum Cables - Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type CL2P or CL3P.

Riser Cables - Cables installed in vertical runs and penetrating more than one floor, or cables installed in vertical runs in a shaft. shall be Type CL2P, CL3P, CL2R, or CL3R,.  There are 2 exceptions to this rule:

1. Other types of cables are allowed if installed in metal raceways or installed in fire rated shafts having fire stops at each floor.

2. Types CL2, CL3, CL2X, and CL3X cable in one- and two-family dwellings.

Other Cables within buildings - Cables installed in building locations other than in plenums, ducts, and other space for environmental air, risers, cable trays, and hazardous locations shall be CL2 or CL3.  There are 5 exceptions to this rule.

The most important exception is the allowing of CL2X and CL3X cables with less than 0.25 inches in diameter to be installed in one-and two-family dwellings.

The next most important exception is allowing CL2X and CL3X cables with less than 0.25 inches in diameter to be installed in NON CONCEALED spaces in multifamily dwellings.