# OFNP vs. OFNR vs. CPR vs. LSZH: The Global Guide to Fibre Cable Jackets

Choosing the right cable jacket is a balance of regional code compliance, material science, and safety priorities. Understanding the difference between NEC and CPR frameworks ensures your network is both resilient and compliant.


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## Global Classification Guide
Selecting the right jacket is a balance between regional code compliance and specific environmental hazards. North American markets prioritize air-handling safety (NEC), while European and Asian markets focus on human toxicity and emission control (CPR/LSZH).

### NEC: OFNP & OFNR [North America]

* The standard for building codes in the US and Canada. Includes Plenum (OFNP) for HVAC spaces and Riser (OFNR) for vertical shafts.
**Features:**
  - OFNP: NFPA 262 Steiner Tunnel Rated
  - OFNR: UL 1666 Flame Propagation Rated
  - Engineered for specific building zones
  - Primarily Fluoropolymer or PVC based

### Euroclass: CPR B2ca/Cca [Europe]

* Mandatory for permanent installations in the EU and UK. Provides individual ratings for smoke, flaming droplets and acidity.
**Features:**
  - Legally required for all permanent EU installations
  - Superior heat release and fire growth protection
  - Ensures safe smoke levels for public building evacuation
  - Protects hardware from acidic combustion byproducts

### LSZH (Low Smoke Zero Halogen) [Asia & Oceania]

* The preferred standard for Asia and Australia. Rated according to IEC 60754 (and sometimes others).
**Features:**
  - Zero Halogen (IEC 60754)
  - Low Smoke (IEC 61034-2)
  - Non-corrosive to GPU/AI server fabrics
  - Ideal for data centers and buildings in Asia


## Regional Safety Benchmarks
Each major global market prioritizes a specific safety metric to define its highest tier of cable infrastructure.

| Metric | Value |
| :--- | :--- |
| USA (OFNP) Flame Limit | **5.0 ft** |
| EUROPE (B2ca) FIGRA | **≤ 20 W/s** |
| ASIA (LSZH) Halogens | **0.0%** |
| GLOBAL (Non-Acidic) | **4.3 pH** |
## The Material Science of Protection
1. **Thermal Resistance**: OFNP jackets use Fluorinated Ethylene Propylene (FEP) with an Oxygen Index >95% to prevent ignition in air.
2. **Endothermic Cooling**: LSZH jackets contain hydrated minerals that undergo an endothermic reaction, releasing water vapor to cool the cable.
3. **Intumescent Char**: Flame-retardant polymers can form a thermally stable char or protective layer during combustion that helps slow heat transfer and reduce flame spread, protecting internal cable components.
4. **Emission Management**: Zero-halogen compounds prevent the formation of corrosive hydrogen chloride (HCl) gas during combustion, reducing toxic and corrosive emissions compared to PVC-based materials.

## Comparison: North American NEC (OFNP/OFNR) vs. European CPR

### North American NEC (OFNP/OFNR)
* Application: Standards defined by NFPA 70 for US/Canadian builds.
* Fire Testing: Focused on the Steiner Tunnel test (NFPA 262).
* Rating: OFNR (Riser) and OFNP (Plenum) ratings for different spaces.
* Environmental: Heavy focus on flame travel and smoke density.

### European CPR
* Application: Mandatory Euroclasses under EN 50575 for EU territory.
* Fire Testing: Focused on FIGRA (Fire Growth Rate) and heat release.
* Rating: Range from Fca to Aca, with a practical limit of B2ca.
* Environmental: Stringent 's, d, a' ratings for smoke, droplets, and acidity.

## Technical FAQ
**Q: Why is 'Zero Halogen' (LSZH) critical for servers?**
A: Standard PVC jackets contain halogens like Chlorine. When burned, they release Hydrogen Chloride gas. In contact with humidity, this forms Hydrochloric Acid, which corrodes electrical equipment. LSZH helps ensure your expensive compute, storage or GPU fabrics remain functional after a minor fire event.

**Q: Can I use OFNR in a plenum space?**
A: No. OFNR (Riser) does not meet the smoke suppression or flame retardancy required for plenums. However, you can use OFNP (Plenum) in a Riser space. For high-density North American builds, we recommend [TightBEND Plenum cables](/en/products/fibre-optic-cables/indoor-cables/tightbend-plenum-tight-buffered-optical-fibre-cables-north-america/) to maintain compliance across all zones.

**Q: Can I use OFNP in a riser space?**
A: Yes. In the North American NEC hierarchy, OFNP (Plenum) is the highest rating and is 'downward compatible' with Riser (OFNR) and General Purpose (OFNG) environments. While you cannot use a Riser cable in a Plenum space, you can use a Plenum cable in a Riser space. Customers specify a plenum cable like [TightBEND Plenum](/en/products/fibre-optic-cables/indoor-cables/tightbend-plenum-tight-buffered-optical-fibre-cables-north-america/) for the entire project to simplify inventory and ensure maximum fire safety throughout the building's vertical and horizontal runs.

**Q: What is the difference between IEC and CPR?**
A: IEC 60332/60754 are the testing methodologies for toxicity and smoke. CPR (EN 50575) is the European legal framework that uses those test results to categorize cables into Euroclasses (B2ca, Cca, etc.). While IEC is a standard, CPR is the law in the EU and UK.

**Q: Why are LSZH cables sometimes stiffer?**
A: To achieve zero-halogen fire retardancy, manufacturers use high concentrations of mineral fillers like Aluminum Trihydrate. This makes the jacket less flexible than standard PVC. To counter this in high-density racks, many customers switch to cables like the range of [SlimCORE micro-cables](/en/products/fibre-optic-cables/indoor-cables/slimcore-indoor-optical-cables/) which optimise bend radius despite the stiffer materials.

**Q: How does the CPR rating impact High-Density AI clusters?**
A: AI clusters generate massive heat. A cable with a low CPR rating (like Dca or Eca) can contribute to a rapid 'flashover' fire. Using higher CPR rated [MPO Trunks](/en/products/optical-cable-assemblies/mpo-trunks/high-fibre-count-mpo-trunks/) provides the necessary thermal barrier and prevents the fire from traveling through cable trays into the heart of the compute fabric.

**Q: What are the 's', 'd', and 'a' suffixes in European Euroclass/CPR cable ratings?**
A: These are additional safety criteria under CPR. The 's' value reflects smoke acidity/density, with 's1' being the highest performance. The 'd' value reflects flaming droplets, with 'd0' meaning 'no flaming droplets' (preventing fire from dripping onto equipment below). The 'a' value reflects gas acidity, with 'a1' indicating the lowest level of acidity.

**Q: Can LSZH cables be used outdoors?**
A: Standard indoor LSZH jackets are not UV-stabilized or water-blocked. For transitions between buildings, you should use an indoor/outdoor rated cable like [SmartRIBBON Indoor/Outdoor](/products/fibre-optic-cables/indoor-cables/smartribbon-ofnr-rated-cpr-rated-optical-fibre-cables/) that features a water-blocked construction.

**Q: Is OFNP the same as LSZH?**
A: Not necessarily. OFNP (Plenum) is a North American fire rating that often uses fluoropolymers (which contain halogens but are highly fire-resistant). LSZH is a material specification (Low Smoke Zero Halogen). You can have an LSZH cable that is NOT Plenum rated, and a Plenum cable that is NOT LSZH. For global projects, ScaleFibre provides [SmartRIBBON dual-rated cables](/en/products/fibre-optic-cables/indoor-cables/smartribbon-flame-retardant-optical-fibre-cables/) that are engineered to meet overlapping international safety criteria.

**Q: How should I handle large cable drums of high-safety rated fibre?**
A: Due to the mineral fillers in high-safety jackets, they are more sensitive to 'kinking' or compression during installation. Always follow our [Cable Drum Handling Guide](/en/resources/cable-drum-handling/) and ensure you don't exceed the minimum bend radius or crush the internal fibres before they are even deployed.


## References
* [1] NFPA 262: Standard Method of Test for Flame Travel and Smoke of Wires and Cables (Plenum).
* [2] EN 50575: Power, control and communication cables - Construction Products Regulation (CPR).
* [3] IEC 60754-2: Determination of acidity and conductivity of gases evolved during combustion.
* [4] UL 1666: Standard for Test for Flame Propagation Height of Cables (Riser).