How do I determine the minimum fire survival time for alarm cables in a specific building?

The required fire survival time is dictated by the building’s evacuation strategy and risk assessment under BS 5839-1. Category L (life protection) and Category P (property protection) systems often specify minimum times: 30 minutes for standard and 120 minutes for enhanced protection. The designer must consider factors like phased evacuation, fire service intervention, and building height. BS 5839-1 Clause 26.2 recommends enhanced cables for unsprinklered buildings over 30 metres tall or where escape routes may be used during firefighting. Always align with the fire engineering plan.