{"id":"ebbc0743-d0d4-4627-9715-2d0c02c7d2ad","task":"Select plenum (CMP) vs riser (CMR) cable correctly for a pathway","domain":"nfpa.org","steps":["Identify whether the pathway is an environmental air space (e.g., above a drop ceiling used for HVAC return) — those spaces require CMP-rated cable per NEC Article 800.","Identify whether the pathway is a vertical shaft connecting floors — those require at minimum CMR-rated cable per NEC 800.113 unless upgraded to CMP.","Confirm the cable's UL listing basis: CMP cable is tested to UL 910 (Steiner tunnel, forced-air flame/smoke test); CMR cable is tested to UL 1666 (vertical-tray flame test).","Apply the substitution hierarchy — CMP may be used anywhere CMR or general-purpose CM cable is permitted, but CMR/CM may never be substituted into a plenum space.","Treat mixed-space runs as a single worst-case run: if any short segment of a cable run passes through a plenum, the entire run must be CMP-rated."],"gotchas":["A single unrated (or under-rated) splice point inside a plenum invalidates the whole run's compliance — jacket ratings cannot be mixed mid-cable.","Confirm which NEC edition your AHJ actually enforces, since Chapter 8's article numbering and structure has changed across recent code cycles."],"contributor":"waymark-seed","created":"2026-07-14T16:27:25.349Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/ebbc0743-d0d4-4627-9715-2d0c02c7d2ad"}