A leading City of London occupier, six storeys, 200 staff, and a fire alarm past the end of its supported life. Gemini AMPM designed, installed, commissioned and certified a hybrid BS 5839-1:2017 L1 system across the whole building in a four-week window — every floor open and trading throughout.
The existing fire alarm pre-dated the current edition of BS 5839-1 and had reached the end of its supported life. Nuisance alarms were disrupting day-to-day operations, and a decade of change — new break-out spaces, additional plant, rising headcount — meant detection coverage no longer reflected how the building was actually used.
The brief left no slack: a fully compliant, modern system across the whole building; no temporary evacuation policy and no simultaneous-evacuation workaround; every floor open and trading throughout; the lot completed within a four-week site window and handed over with full certification and a planned maintenance schedule. Occupied-building work, in other words — with the emphasis on occupied.
An intelligent analogue addressable control panel with a hybrid loop: wired backbone, wireless translators serving the open-plan floors, and optical, multi-criteria and heat detectors selected per zone risk profile. L1 detection coverage to BS 5839-1:2017 throughout, with manual call points at every final and storey exit.
The new system was integrated with the building’s existing PAVA and BMS. One contract covered design, installation, commissioning, certification and the 28-day defects period — a single point of accountability from the first survey to the final signature, with a planned maintenance schedule agreed at handover.
Phased night shifts and selected daytime hours, coordinated directly with the facilities manager and tenant representatives floor by floor. Cable runs routed to spare the ceiling grid, wireless devices fitted without disturbing a single desk, and each floor tested and signed off before the team moved to the next.
Handover with a full BS 5839-1 commissioning certificate, complete O&M documentation and an ongoing planned maintenance contract under Gemini AMPM’s national servicing programme. Standardised, in-stock components reduce the future maintenance footprint, and the wireless platform expands as floor layouts evolve.
A fresh survey and a review of the fire risk assessment led to a hybrid answer: a wired backbone with wireless detection across the tenant floors, cutting containment work above false ceilings and letting cellular offices and meeting rooms come online without disturbing the neighbours. Engineers worked phased night shifts and selected daytime hours, floor by floor — each one tested, certificated and signed off before the team moved up. Wireless devices arrived pre-programmed, cutting in-room install time by roughly 60%.
The works landed inside the four-week window without a single lost workday. The building now runs L1 coverage to BS 5839-1:2017, the nuisance alarms are gone, and over 200 employees sit on a modern, monitored platform — handed over with a full commissioning certificate, O&M documentation and a planned maintenance contract.
PQQ-ready evidence and client references behind this project are available on request. A named engineer, not a call centre, comes back within 24 hours.