Why false alarms are now a board-level fire-safety issue
False alarms don’t just waste minutes. They train people to hesitate, creating “alarm fatigue” that can slow evacuation when an alarm is genuine. Nationally, the scale is large: in England, Fire and Rescue Services attended 251,479 fire false alarms in the year ending September 2025, and fire false alarms accounted for 39% of all incidents attended.
In London, the pressure has even reshaped response policy. London Fire Brigade reports that in 2023/24, automatic fire alarms accounted for almost 40% of its callouts (around 52,000), and that 99% of commercial automatic alarm calls were later recorded as false alarms. The Brigade also warns that repeated unwanted alarms erode confidence in fire alarm systems and increase avoidable risk during unnecessary emergency journeys.
This is the real promise of modern detection: not simply “faster”, but more believable - so the signal keeps its authority when it is life-critical.
Standard smoke alarms: good at one signal, vulnerable to many lookalikes
A “standard smoke alarm” is typically a single-criterion device: it triggers when its smoke sensing element reaches a preset threshold. In domestic settings, smoke alarms are commonly designed and certified to BS EN 14604, a product standard intended for household (or similar residential) applications.
The limitation is built into the physics. If a device is looking for one signature (smoke), then some non-fire phenomena can still look “smoke-like” to the sensor: steam, cooking vapour, dust, aerosol sprays, and some types of contractor activity. This is why false-alarm reduction guidance leans heavily on correct siting and on reviewing detector selection when conditions change. The Fire Industry Association cautions, for example, that smoke detectors should not be sited near sources of steam (such as kettles or shower cubicles), and emphasises that detection type and siting should be reviewed if the environment, risk, or use changes.
One more trap: “turning down sensitivity” can feel like an easy fix, but it has consequences. The same FIA guidance warns that reducing detector sensitivity delays response to a real fire.
Multi-sensor fire detectors: what’s different, and why it matters
Modern multi-sensor (multi-criteria) fire detectors combine two or more sensing elements, typically smoke + heat, and increasingly smoke + heat + carbon monoxide (CO) - and use an algorithm to decide whether the pattern of signals is consistent with fire or nuisance. Industry guidance defines a multi-sensor detector as using more than one sensor to respond to one or more fire phenomena and explains that dedicated European test standards exist for these multi-sensor combinations.
Those multi-sensor point detector standards include EN 54-29 (smoke + heat) and EN 54-31 (smoke + CO, optionally heat).
In commercial installations, the benefits multiply again when the devices are addressable: each detector has a unique address, allowing the system to report the exact alarm location and support better maintenance and diagnostics.
How multi-sensors reduce false alarms while improving detection reliability
Multi-sensors cut unwanted alarms by moving from “one threshold” to multiple signals + trend logic. A transient aerosol might generate a smoke-like optical signal, but it usually doesn’t evolve into the heat rise and/or CO signature you would expect from a developing fire. Multi-sensor algorithms can use that difference to wait when they should, and act when they must.
Independent testing supports that mechanism. The Building Research Establishment tested 35 optical/heat multi-sensor detectors alongside reference optical smoke detectors across ten test fires and five false-alarm tests designed around common nuisance sources (toast, cooking, water mist, dust, aerosols). BRE reports that fire response performance was broadly similar between multi-sensors and optical smoke detectors, but across all five false-alarm tests the multi-sensors, on average, operated later than the reference optical smoke detectors, sometimes not operating at all by the end of the false-alarm test.
That “later operation” is not a weakness; it is the point. BRE describes this as increased resistance created by delaying the response to transient smoke-like phenomena, giving time for the nuisance source to die away or be dealt with before an unwanted alarm is triggered.
There is an important reality check here that good specifiers take seriously: multi-sensors are not all the same. BRE notes that false-alarm resistance depends on the specific design features and implementation, and it cannot be assumed that any multi-sensor detector will significantly reduce false alarms from every form of “fire-like” phenomenon.
Field investigations point in the same direction, with appropriate caution. In a BRE review of live unwanted fire alarm investigations, none of the false alarms observed in the study sample were attributed to multi-sensors; however, BRE stresses that conclusions are limited without knowing the proportion of multi-sensors installed and that configurations and modes vary.
CO sensing can strengthen both early detection and discrimination in certain scenarios. A white paper from Euralarm explains that CO fire detectors can react promptly to smouldering fires and may be better suited where other techniques are prone to false alarms (for example, dust, steam, and cooking vapours). It also states that multi-sensor point detectors improve accuracy by assessing multiple criteria, thereby reducing false alarms.
The underlying principle is supported in research published via the National Institute of Standards and Technology: combining smoke measurements with CO measurements in specific algorithms can reduce false alarms while increasing sensitivity (shorter detection time for real fires).
Standards and compliance in the United Kingdom: what “latest” really means
For non-domestic premises, the current code of practice for fire detection and fire alarm system design, installation, commissioning, and maintenance is BS 5839-1:2025, published by the British Standards Institution.
Guidance summarising the 2025 revision highlights a greater emphasis on multi-sensor detectors: where point smoke detectors may present a higher risk of false alarms, the revision recommends selecting multi-sensor detectors instead (with detector selection guidance in Annex D).
For specifiers who want system-level confidence (not just compliant parts), EN 54-13 is focused on compatibility/connectability assessment and system integrity, providing evidence that the complete system will function as intended under expected operating conditions.
Choosing the right addressable multi-sensor and where to start
Multi-sensors create their biggest impact where nuisance sources are common: kitchens/servery-adjacent circulation spaces, steam-prone areas, dusty environments, and buildings with strong temperature swings or frequent aerosol use. The practical playbook is straightforward: match the sensor mix (smoke+heat or smoke+heat+CO) to your risks and nuisance profile, then configure modes and sensitivities to the real environment and review it when the environment changes.
Inbuild UK’s addressable multi-sensor range includes:
- Smoke & heat devices with selectable modes and variable sensitivity (for example, the Hochiki ACC-EN family, which is panel-selectable across optical-only, heat-only, or combined operation).
- Addressable combined smoke/heat models designed to EN 54 parts 5 and 7 (for example, Zeta Fyreye MkII combined smoke & heat variants).
- Smoke/heat/CO multi-sensors with multiple approved operating modes (for example, Hochiki multi-sensors with CO).
- Programmable multi-sensors with multiple detection modes, time-of-day sensitivity options, drift compensation, and algorithms designed to improve tolerance to false alarms while improving detection of real fire conditions (for example, C-TEC CAST PRO).
