Flame-retardant duct optical cable

For optical cables inside ducts, flame-retardant indoor cables with LSZH or plenum-rated jackets are recommended to ensure fire safety and compliance with building codes.

Cable Types and Fire Ratings

Plenum-rated cables (OFNP/OFCP) are designed for the highest fire resistance, suitable for air-handling spaces and ducts where smoke and flame spread must be minimized. They are tested to stringent standards such as NFPA-262 or UL-910, which measure flame propagation and smoke density during extended burns . Riser-rated cables (OFNR) are suitable for vertical runs in riser shafts between floors. They prevent flame propagation along the cable but are less strict than plenum-rated cables, making them appropriate for ducts that are not part of air-handling systems . General-purpose cables (OFNG) are used in areas with lower fire risk and are not recommended for critical duct installations where fire safety is a concern .

Jacket Materials

Low Smoke Zero Halogen (LSZH) jackets are highly recommended for indoor duct installations. LSZH cables emit minimal smoke and no halogens when burned, reducing toxic gas exposure in confined spaces . PVC jackets are flame-retardant and cost-effective but may emit toxic gases when burned, making them less suitable for enclosed ducts in public or high-occupancy buildings . HDPE or LDPE jackets are more common for outdoor or flexible applications but can be adapted for indoor ducts if flame-retardant additives are included .

Specialized Duct Solutions

Some manufacturers offer fire-retardant microducts or DuraOpto Fire Retardant ducts, which provide a protective pathway for fiber optic cables in indoor FTTH, data centers, tunnels, and transportation networks. These ducts are made from high-quality HDPE and are optimized for end-to-end fiber jetting while maintaining fire safety . For tighter indoor conduits, LSZH FTTH drop cables are recommended due to their small form factor, halogen-free composition, and flame-retardant properties .

Installation Considerations

• Always verify the cable's fire rating against local building codes and NEC/NFPA standards.
• Use plenum-rated cables in ducts that are part of air-handling systems.
• For vertical riser shafts, riser-rated cables are sufficient.
• Ensure proper mechanical protection and routing to prevent damage during installation, especially in long horizontal runs or tight bends .
• Request test certificates from recognized labs (UL, Intertek, NRTL) to confirm flame-retardant performance . By selecting the appropriate flame-retardant cable type and jacket material, you can ensure safe, code-compliant fiber optic installations inside ducts while minimizing smoke and toxic gas hazards.