Cables and connections
CL2 / CL3 rating
Fire-safety ratings for low-voltage cable jackets that make speaker and HDMI runs legal to install inside walls and ceilings.
CL2 and CL3 are UL classifications for Class 2 and Class 3 low-voltage circuits under the National Electrical Code. The rating certifies the jacket's flame resistance and smoke behavior. CL3 is rated for slightly higher voltage and can be used anywhere CL2 is required.
Any cable run inside a wall, ceiling, or floor cavity must carry an in-wall rating in most jurisdictions, so it matters as soon as you hide speaker wire or HDMI. Ordinary zip cord and unrated HDMI jackets are not permitted in concealed spaces.
Look for CL2 or CL3 printed on the jacket. Use CL2P/CL3P plenum cable in air-handling spaces such as return-air drop ceilings, and riser (CL2R/CL3R) between floors. In-wall rated 14 or 16 AWG OFC covers almost every home speaker run.
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