A fiber cable’s fire rating isn’t a quality marker — it’s a code requirement. Installing OFNR cable in a plenum space will fail inspection and require costly replacement. This guide explains the rating systems and how to specify correctly.
NEC Ratings (North America)
| Rating | Application | Flame Spread |
|---|---|---|
| OFNP | Plenum (air-handling spaces) | Lowest |
| OFNR | Riser (vertical shafts) | Low |
| OFNG | General purpose (horizontal, single floor) | Moderate |
IEC Ratings (International)
IEC 60332 defines flame spread categories (A, B, C, D). IEC 61034 defines smoke density. LSZH (Low Smoke Zero Halogen) is specified under IEC 60754 for halogen content and IEC 61034 for smoke.
Related Reading: Indoor fiber cables · Single vs multi-mode
Key Takeaways
- OFNP is required in plenum spaces. OFNR in plenum will fail inspection.
- LSZH is mandatory in EU, Middle East, and transit tunnels. Check local building codes.
- The rating must match the installation environment, not the equipment room.
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