Fire Detection in Open-Plan Offices
Open-plan offices seem like the easy case — a big clear space, a grid of detectors, done. In reality they are among the most frequently reconfigured spaces in any building: partitions go up, pods appear, storage rises, and the layout the detection was designed for quietly disappears. The challenge is not the original design but keeping coverage valid as the space churns. This guide covers what makes open-plan detection distinctive and what to check.
The recurring theme is that the detection must protect the office as it is now, not as it was on the day it was commissioned.
Who this is for
This is for competent fire alarm engineers designing or maintaining detection in open-plan offices. The experience level assumed is competent engineer. Use it for the principles; the specific coverage and spacing come from the fire risk assessment and BS 5839-1 for the actual ceiling and layout.
Why open-plan is distinctive
Open-plan offices look simple to protect, but they are reconfigured often — new partitions, meeting pods, high storage and changed layouts — and each change can disturb detector coverage. The detection has to suit the current layout, not the one it was designed for. Coverage and spacing follow the fire risk assessment and BS 5839-1, and the defining issue in these spaces is keeping those valid through a constant churn of change. An office that has been fitted out several times since commissioning may have detection that no longer matches the floor.
Partitions and fit-outs
Fit-outs are where coverage quietly degrades. Adding full-height partitions can create new rooms or enclosures that need their own detection; new ceilings, high furniture or storage can obstruct detectors or change how smoke reaches them. A fit-out that ignores the fire alarm can leave areas under-protected without anyone noticing. So any layout change should trigger a review of detection coverage against the fire risk assessment and BS 5839-1 — the fire alarm needs to be part of the fit-out, not an afterthought discovered at the next service.
Coverage still applies
It is tempting to think an open space needs less detection, but that is not how it works. Detector coverage still follows the spacing and coverage principles in BS 5839-1 for the category and the ceiling, and features such as beams, voids and high storage can reduce effective coverage rather than increase it. From field experience, high racking and full-height screens are common causes of coverage that looks fine on a plan but isn't in reality. The number and siting come from the design against BS 5839-1, applied to the actual ceiling and layout.
Servicing open-plan detection
Servicing an open-plan office is largely about reconciling the detection with the current space. Confirm detector coverage still suits the layout, that partitions or fit-outs added since have not created uncovered enclosures or obstructed detectors, and that the system matches the space as it is now. From field experience, detection not updated after a churn of fit-outs is the classic finding — small changes accumulating into real gaps. Record coverage concerns and flag any area left under-protected.
Common points to check
Recurring issues include new partitions creating uncovered enclosures, detectors obstructed by high storage or screens, and coverage not updated after fit-outs. Confirming coverage still suits the current layout is the essential check.
When not to rely on this alone
When not to use this article: do not use it to design detector coverage for a specific office. That comes from the fire risk assessment and BS 5839-1, applied by competent professionals to the actual layout.
Relevant standards
Coverage and spacing follow BS 5839-1, a code of practice, within the fire risk assessment. The legal duty for fire precautions in most non-domestic premises sits under the Regulatory Reform (Fire Safety) Order 2005, with Building Regulations statutory guidance in Approved Document B applying to building work. Separate the legal duty from the recommended methods, and always work to current editions.
Professional disclaimer
This is an educational and workflow resource for competent engineers and does not replace the current British Standards, the fire risk assessment, or competent judgement. Verify coverage against current documentation and the actual layout.
Related documentation
Use this with the current BS 5839-1 and the fire risk assessment. Record coverage against the current layout, and review detection whenever the office is reconfigured or fitted out.