The Fire Industry Association (FIA) has released concise new guidance to clarify the correct use of fire alarm system categories under BS 5839-1 (2025). This is a revised version based on the 2025 update to BS 5839-1.

Despite the categories remaining unchanged for many years, confusion persists over their application and critically who is responsible for selecting the appropriate category. The guidance makes clear that this responsibility sits with the fire safety specialist, not the fire alarm system designer or contractor.

Covering Categories M, L1–L5 and P1–P2, the document explains their purpose, typical applications across different building types, and highlights key updates in the 2025 standard, including the preference for non-heat detection in sleeping accommodation. It also reproduces Annex A of BS 5839-1, offering insight into established custom and practice.

This short, practical guide will help improve specification clarity, reduce disputes, and support compliance with fire safety legislation.