Cable Fire Propagation — Single Cable vs. Bunched Test

The distinction between two cable fire-testing methods that are often confused: IEC 60332-1 tests whether a single, vertically suspended cable self-extinguishes after exposure to a gas flame for a set time (the flame must not propagate beyond a specified distance along the cable), whereas IEC 60332-3 simulates a more realistic scenario in which multiple cables are bundled — as in a cable tray or on a cable ladder in practice — suspended vertically and exposed to a flame. A cable that successfully passes the IEC 60332-1 test often still fails the IEC 60332-3 bunched test, because the stacking of combustible cable sheath materials in a bundle causes a much greater thermal load and an increased risk of flame propagation via neighbouring cables than is the case with an isolated cable. For applications where multiple cables are laid close together in cable trays or ladders, NEN 1010 and building regulations therefore prescribe bunch-tested cables (or an equivalent fire-resistant measure), even if the individual cable already passes the simpler single-cable test.