Fire Resistant Ethernet Cable: The Rating Explained
Quick answer / TL;DR: Short answer: for flame spread and smoke in occupied spaces, choose the jacket rating the space requires – CMP in plenums, CMR in risers, and low-smoke zero-halogen (LSZH) where specified. For a circuit that must keep operating during a fire, you need a circuit-integrity rated cable, which is a different and much more expensive product. Ask which of the two the project means before ordering.
Fire resistant ethernet cable is asked for in two different situations that are often confused: a route through a space where cable must not spread flame, and a circuit that must keep working during a fire. The first is a jacket rating; the second is a circuit-integrity rating, and they are not the same product.
This is the rating guide: what each requirement means, the codes involved, and the questions that decide which cable a project actually needs.
Two Requirements, Two Products
| The requirement | The property | The product |
|---|---|---|
| Flame spread | Limits fire travel along the cable | CMP, CMR, LSZH jackets |
| Smoke and halogen | Reduces toxic smoke | LSZH compounds |
| Circuit integrity | Keeps working during a fire | Fire-rated cable with a barrier |
| Firestop | Seals the penetration | A system, not a cable |
The first two are jacket properties used every day; the third is a specialist product for life-safety circuits and is not what most projects mean by the phrase.
The Jacket Codes
- CMP: plenum rated – the highest flame and smoke performance in the common family
- CMR: riser rated – for vertical shafts between floors
- CM: general purpose – not for plenums or risers
- LSZH: low smoke zero halogen – common where smoke toxicity matters
The codes are route permissions, not guarantees: the space decides which one applies.
Where Each Is Required
| The space | The typical requirement |
|---|---|
| Air-handling plenum | CMP |
| Vertical riser shaft | CMR |
| General office ceiling | CM or CMR |
| Public transport, tunnels | LSZH or project-specific |
| Life-safety circuit | Circuit-integrity rated cable |
Standards and Verification
| The reference | The relevance |
|---|---|
| UL 444 / NEC Articles 800 and 725 | Jacket ratings and permitted routes |
| IEC 60332 | Flame propagation test methods |
| IEC 60754 / 61034 | Halogen and smoke tests |
| Local building code | The authority for the specific space |
Per-market fire requirements are not provided in the knowledge base. The rating families are standard; confirm the requirement with the local authority rather than assuming a code transfers between countries.
Real-World Applications
The plenum ceiling
A return-air ceiling used as a plenum: CMP cable throughout – the jacket that limits both flame spread and smoke in the air path.
The tunnel project
A transport tunnel specifying LSZH: low-smoke compound on every data cable, documented per reel – the smoke requirement driving the specification, not the bandwidth.
The misread requirement
A client asking for fire resistant cable meaning plenum-rated: the requirement clarified before ordering. CMP delivered at a fraction of the circuit-integrity price – the phrase had hidden two different products.
Related reading: The jacket ratings in full? Read the cable jacket ratings guide — blogs/news/cable-jacket-ratings
Related reading: Where the plenum rating fits a route? Read the Cat6 riser cable guide — blogs/news/cat6-riser-cable
Frequently Asked Questions
What is fire resistant ethernet cable?
A cable built to resist flame spread, or – separately – one rated to keep working during a fire. The two are different products.
Is CMP the same as fire resistant?
CMP is a plenum jacket rating for flame and smoke. It is not a circuit-integrity rating.
What is LSZH?
Low smoke zero halogen: a jacket compound that produces less toxic smoke, common in tunnels and public buildings.
Do I need fire-rated cable for a life-safety system?
Yes – a circuit-integrity rated product, specified by the system designer, not a standard data cable.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.