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IEC 60331-25: Fire-Resisting Cables — The “Lifeline” Maintaining Circuit Integrity During Fire
When Fire Breaks Out, Emergency Lighting and Fire Pump Cables Must Keep Working — For How Long?
IEC 60331-25:1999 specifies fire-resisting cables (cables maintaining circuit integrity under fire conditions). Unlike flame-retardant cables (IEC 60332, preventing flame propagation), fire-resisting cables must continue functioning during a fire — a mandatory requirement for fire pumps, emergency lighting, smoke extraction fans, and fire alarm system cables.
| Standard | Cable Type | Test Requirement | Application |
|---|---|---|---|
| IEC 60332 | Flame-Retardant | Single wire, no flame propagation | General building wiring |
| IEC 60331 | Fire-Resisting | 750–950°C flame + mechanical shock, maintain circuit integrity | Fire safety equipment supply |
The core technology: mica tape wrapped between the conductor and XLPE insulation. Mica (KAl₂(AlSi₃O₁₀)(OH)₂) has a melting point exceeding 1,200 °C and forms a ceramic-like insulating layer under fire conditions. The mica tape overlap ratio and thickness are the core manufacturing parameters determining fire survival time.
TNLab — Flame-retardant cables slow fire spread. Fire-resisting cables keep critical equipment running during a fire. They are not the same thing.
