What performance criteria distinguish fire-resistant cables from flame-retardant variants, and how do their structural designs address distinct safety requirements?

Fire-resistant cables prioritize circuit continuity during combustion, utilizing specialized materials such as mica tape wraps and heat-stable copper conductors to maintain functionality for specified durations (usually 1–3 hours) when exposed to flames reaching 950–1000°C. This design ensures critical systems like emergency lighting and fire alarms remain operational during building evacuations. In contrast, flame-retardant cables focus on limiting fire spread through halogen-free or low-smoke additives that suppress flame propagation and toxic gas release, though they may cease to function electrically once insulation reaches thermal degradation temperatures.   Structural differences are notable: fire-resistant models integrate multiple protective layers, including intumescent barriers that expand to insulate conductors, while flame-retardant versions depend on modified polymer compounds with self-extinguishing properties. Installation environments dictate selection—fire-resistant cables are suited for escape routes and life safety systems, whereas flame-retardant types are standard in general building wiring to minimize fire growth potential. Both categories undergo rigorous testing, with fire resistance validated through temperature-time curve exposure and flame retardancy measured via vertical flame spread indices.