RBishop

BS 5839-1:2025 is fairly clear on this point. The standard states that external joints should be avoided wherever practicable, but where they are necessary, the jointing method and terminals need to be capable of withstanding a similar temperature and duration to that of the cable itself. In other words, the joint shouldn’t become the weak point in the fire-resisting cable system. It also requires joints outside system components (panels, detectors, MCPs, sounders etc.) to be enclosed in suitably labelled junction boxes, with the intention being that they remain identifiable and maintain integrity during fire conditions. That’s why you’ll commonly see: metal junction boxes ceramic terminal blocks fire-resistant terminals/fixings used on life safety systems, rather than generic plastic choc-boxes or floating connector strips above ceilings.