Cable Selection
OFNP vs OFNR vs LSZH: Fiber Cable Fire Ratings for US and EU Projects
OFNP, OFNR and LSZH are fire-performance ratings for a fiber cable's jacket — and they are not interchangeable, because they come from two different regulatory systems. OFNP (plenum) and OFNR (riser) are US ratings under the NEC/NFPA, ranked by flame spread. LSZH (low-smoke zero-halogen) is a material property tied to the EU's CPR system, ranked by smoke and acidity. A cable can be OFNP-rated and not LSZH, or LSZH and not plenum-rated. Specifying the wrong one does not just fail an inspection — in the US it can be a code violation, and in the EU it can bar the product from the project entirely.
Key takeaways
- OFNP > OFNR. Plenum outranks riser; you can substitute OFNP where OFNR is required, never the reverse.
- US and EU are different systems. OFNP/OFNR answer "flame spread" (NFPA); CPR Euroclass answers "smoke + acidity + heat release." One does not convert to the other.
- LSZH is a material, not a US fire rating. A cable can be LSZH yet carry no plenum rating — and a plenum (OFNP) cable is often not LSZH.
- For EU projects, ask for the CPR Euroclass and the DoP (Declaration of Performance), not "LSZH." Euroclass is the thing building control checks.
- Sourcing reality: a supplier that holds both UL (OFNP/OFNR) and CPR certification can serve US and EU builds from one product line. Most cannot.
The US system: OFNP vs OFNR (and OFNG/OFN)
US fiber fire ratings come from the National Electrical Code (NFPA 70), Article 770. They classify a cable by where in a building it may legally run, based on how far flame spreads along it and — for plenum — how much smoke it produces. From highest to lowest:
Rating | Use | Test | Substitution |
|---|---|---|---|
OFNP | Plenum — air-handling spaces (above drop ceilings, raised floors) | NFPA 262 | May replace OFNR, OFNG, OFN |
OFNR | Riser — vertical shafts between floors | UL 1666 | May replace OFNG, OFN |
OFNG / OFN | General-purpose — single floor, non-plenum | UL 1685 | Lowest — no substitution up |
The "OFN" prefix is optical fiber nonconductive — the all-dielectric construction with no metallic elements, which is the common case for fiber. (Cables with a metallic strength member or armor take the OFC "conductive" family instead.) The one rule to remember: substitution flows downward only. Plenum cable satisfies a riser requirement; riser cable in a plenum is a code violation, because the plenum smoke test (NFPA 262) is the stricter bar and riser cable was never held to it.
Why plenum is strictest: a plenum is a space that moves building air. A cable burning there feeds smoke straight into what everyone breathes, so NFPA 262 limits both flame travel and smoke density. A riser fire, by contrast, is dangerous mainly because a vertical shaft acts like a chimney — UL 1666 tests that flame does not propagate floor-to-floor — but smoke is not part of that pass/fail.
The EU system: CPR Euroclass and why LSZH is not enough
Europe does not use OFNP/OFNR. Since the Construction Products Regulation (CPR) took effect for cables in 2017, any cable permanently installed in an EU building carries a Euroclass reaction-to-fire rating under EN 13501-6, declared on a Declaration of Performance (DoP). The main classes for cable, best to worst:
Euroclass | Performance | Typical use |
|---|---|---|
Aca | Non-combustible (essentially only mineral cables) | Rare for fiber |
B2ca | Very limited heat release and flame spread | High-rise, hospitals, transport hubs, escape routes |
Cca | Limited flame spread | Public/commercial buildings |
Dca | Basic flame spread limit | General buildings |
Eca | Minimum entry class | Low-risk / lower-requirement installs |
Two supplementary classifications ride alongside the main class and are often what a specification actually pins down: s for smoke (s1 lowest → s3), d for flaming droplets (d0 none → d2), and a for acidity (a1 lowest → a3). A real spec reads like B2ca-s1a1, not just "B2ca."
Here is the trap. "LSZH" is a jacket material property — low smoke, zero halogen — not a Euroclass. LSZH describes what the jacket is made of and how it behaves (little smoke, no corrosive halogen acid gas when it burns), which maps to the s and a supplements. But a cable being LSZH tells you nothing about its main-class flame spread. You can have an LSZH cable that only reaches Eca. Conversely, achieving B2ca almost always requires LSZH materials, but the rating is the claim, not the material. For an EU project, specify the Euroclass (e.g. B2ca-s1a1) and demand the DoP — never accept "it's LSZH" as the answer.
OFNP vs LSZH: the mistake exporters actually make
Because US and EU systems measure different things, the two ratings do not translate — and the gap runs both ways:
OFNP (US plenum) | LSZH / high Euroclass (EU) | |
|---|---|---|
Governs | Flame spread + smoke in air-handling spaces | Heat release, smoke production, acidity, droplets |
Jacket often is | FEP or other fluoropolymer (contains halogen) | Halogen-free compound |
Halogen-free? | Usually not — plenum compounds are typically halogenated | Yes, by definition |
Plenum-rated? | Yes | Not necessarily — LSZH ≠ plenum |
So a US plenum cable is frequently not low-smoke-zero-halogen, and a European LSZH cable is frequently not plenum-rated. There is a hard technical reason the two often exclude each other: plenum performance is usually reached with fluoropolymer (FEP) compounds, which contain halogen — the exact thing a high CPR class with an a1 acidity requirement is written to keep out. So a genuine OFNP jacket can be structurally disqualified from a low-acidity Euroclass, and a genuine B2ca-s1a1 jacket may never have faced the NFPA 262 plenum test. A buyer who ships a US-plenum cable to a German hospital, or an LSZH cable into a US plenum, has bought a cable that fails the local requirement despite carrying a legitimate fire rating from the other continent.
Because the two systems do not convert, the only safe way to read a cross-border requirement is side by side:
United States (NEC / NFPA) | European Union (CPR) | |
|---|---|---|
Rating on the cable | OFNP / OFNR / OFNG / OFN | Euroclass Aca–Fca + s/d/a supplements |
Ranked by | Flame spread; smoke for plenum | Heat release, flame spread, smoke, droplets, acidity |
Key tests | NFPA 262 (plenum), UL 1666 (riser) | EN 50399, EN 13501-6 |
Document to demand | UL certificate / listing | Declaration of Performance (DoP) |
"Low smoke / halogen-free"? | Not required; plenum is often halogenated | Captured by the s and a supplements |
Converts to the other? | No. There is no equivalence — an OFNP cable is not "a Euroclass," and B2ca is not "a US rating." | |
This is the single most common fire-rating error in cross-border fiber procurement, and it is why "what fire rating do you need?" is really two questions: which country, and which space.
What this means for sourcing
The practical consequence is a supplier question. A cable jacket qualifies for OFNP/OFNR only if the manufacturer holds the corresponding UL certification and builds to it; it qualifies for a CPR Euroclass only if the manufacturer holds CPR certification and can issue the DoP. These are separate audits, separate test regimes, and separate certificates. A trading company reselling cable holds neither — it can forward a mill's paperwork at best, and cannot issue a DoP in its own name.
DYS holds both. On the US side, UL certification (UL LLC, since 2019) covers the OFNP/OFNR jackets. On the EU side, CPR certification was obtained in three successive classes — Eca (2018), Dca (2019), and B2ca (2023) — climbing the Euroclass ladder to the class demanded by high-rise and public-building work. That means one manufacturer can supply a UL-certified plenum/riser build for a US project and a CPR-certified build up to B2ca for an EU project — each qualified under its own system rather than one rating being passed off as the other. The indoor line ships in PVC, OFNR, OFNP and LSZH jackets, and the correct fire class is confirmed per market against the certificate that governs it, not inferred from the jacket material. For a buyer serving both regions, that removes the usual choice between two suppliers — or the usual risk of one supplier quietly substituting a rating it cannot actually certify.
Two questions settle it on any RFQ: "Do you hold the UL certificate for this OFNP/OFNR construction?" and "Can you issue a CPR DoP at the Euroclass we need?" If the answer to either is a forwarded third-party document rather than the supplier's own certificate, you are buying the paperwork, not the compliance.
Choosing a rating
- US, above a drop ceiling or under a raised floor — OFNP. No exceptions; it is an air-handling (plenum) space.
- US, vertical riser between floors — OFNR minimum. OFNP is a legal substitute if you are standardizing on one cable.
- US, single floor, not plenum — OFNG/OFN is compliant, though many specs default up to OFNR for consistency.
- EU, general building — Cca or Dca per local rule; confirm the required s/d/a supplements.
- EU, high-rise / hospital / transport / escape routes — B2ca, typically B2ca-s1a1. Get the DoP.
- Serving both regions — source from a manufacturer that certifies to both systems, so a single line covers both builds. See the cable selection guides for construction choices, and the DYS indoor cable range for the jacket options.
Frequently asked questions
What is the difference between OFNP and OFNR?
Both are US (NEC/NFPA) fiber cable fire ratings. OFNP is plenum-rated for air-handling spaces and tested to NFPA 262, the stricter test covering flame spread and smoke. OFNR is riser-rated for vertical shafts between floors, tested to UL 1666 for floor-to-floor flame propagation. OFNP outranks OFNR and can be substituted for it; the reverse is a code violation.
Is LSZH the same as OFNP?
No. OFNP is a US plenum fire rating based on flame spread and smoke. LSZH (low-smoke zero-halogen) is a jacket material property associated with the EU/CPR system, based on smoke production and acidity. A plenum (OFNP) cable is usually made of halogenated fluoropolymer and is often not LSZH; an LSZH cable is often not plenum-rated. They are not interchangeable.
Can I use an OFNR cable in a plenum space?
No. Plenum spaces require OFNP, which passes the stricter NFPA 262 test. Riser (OFNR) cable has only passed UL 1666 and is not rated for the smoke performance a plenum demands — installing it there is a code violation. Substitution only flows downward: plenum for riser, never riser for plenum.
What Euroclass do I need for a European project?
It depends on the building. General buildings are typically Cca or Dca; high-rise, hospitals, transport hubs and escape routes usually require B2ca, often specified as B2ca-s1a1 (with the smoke and acidity supplements). The requirement is set by local building control — confirm it, then demand the cable's Declaration of Performance (DoP) at that class.
Does LSZH mean the cable is fire-rated?
Not on its own. LSZH tells you the jacket produces little smoke and no corrosive halogen gas when it burns — the s and a parts of a Euroclass — but it says nothing about flame spread, which is the main class. An LSZH cable could still be only Eca. Always specify the full Euroclass, not just "LSZH."
Do US and EU fire ratings translate to each other?
No. They measure different things — US ratings rank flame spread by installation space, EU Euroclass ranks heat release, smoke, droplets and acidity — and there is no conversion between them. A cable certified for one market is not automatically compliant in the other. Cross-region projects need cable certified to each region's system, which is why dual UL + CPR certification matters when sourcing.
Who can issue a CPR Declaration of Performance?
The manufacturer that holds the CPR certification for that cable, based on testing by a notified body. A trading company or reseller cannot issue a DoP in its own name — it can only pass along a mill's document. On EU-bound orders, confirm the supplier can issue the DoP itself at the Euroclass you require.