Plenum-rated cable

networking

Stands for: Plenum and riser cable ratings (CMP/CMR)

The fire rating that decides where a cable may legally run - plenum (CMP) for air-handling spaces, riser (CMR) for vertical shafts.

Air-handling plenums spread smoke fast, so cable jacketed for those spaces (CMP) must burn slowly and emit little smoke; riser-rated CMR handles floor-to-floor shafts; general-purpose ratings cover the rest. Ratings nest downward - plenum can substitute for riser, never the reverse. Outside North America the parallel vocabulary is LSZH (low smoke, zero halogen). It is the code-compliance dimension of cabling, enforced by inspectors rather than by link testers.

Also known as: plenum, cmp, cmr, riser cable, lszh

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