Ajax HazeFlow 2 Fire Detection: Why It Matters for False-Alarm-Prone Sites
Ajax HazeFlow 2 Fire Detection: Why It Matters for False-Alarm-Prone Sites
Published 8 May 2026 · Last updated 8 May 2026 · By Netview
False alarms are the single most expensive nuisance on a UK fire system. Each one costs the customer goodwill, costs the installer a site visit, and on monitored systems risks fines from the local fire and rescue service. Hikvision-style optical smoke detectors and older single-spectrum heads cannot tell water vapour from a real fire, and that's exactly the gap Ajax's HazeFlow 2 algorithm is built to close. This guide is for UK installers who fit Ajax wireless fire alongside CCTV and intruder, and need to know where HazeFlow 2 saves you call-outs, where it changes nothing, and which Ajax SKUs to pair it with on residential and EN54 commercial jobs.
At a glance
- HazeFlow 2 is Ajax's smoke-detection software algorithm. It runs on every FireProtect 2 wireless detector and analyses output from a dual-spectrum optical chamber to confirm real smoke before raising an alarm.
- The chamber uses a blue LED and an infrared LED at different wavelengths to size each volatile particle, distinguishing combustion smoke from cooking aerosol, water vapour and dust.
- FireProtect 2 carries the BSI Kitemark, UKCA and CPR approvals required for UK domestic and small-commercial installs that fall under BS 5839-6 and EN 14604.
- For EN54-certified life-safety on commercial sites you still pair the certified EN54 FireProtect range with the EN54 Fire Hub Jeweller; HazeFlow 2 is the residential / small-business algorithm.
- Place FireProtect 2 on ceilings 4.5 m or less from any sleeping area, keep it 300 mm clear of light fittings, and never inside bathrooms, en-suites or directly above hobs.
What is Ajax HazeFlow 2?
HazeFlow 2 is the proprietary software algorithm that processes signals from the dual-spectrum optical chamber inside every Ajax FireProtect 2 detector. Where a single-LED optical detector simply asks "is there enough scatter to trigger?", HazeFlow 2 looks at how the scatter behaves across two wavelengths over time, then matches the pattern against fire signatures before it raises a confirmed alarm.
The algorithm runs continuously on the detector itself — not in the cloud, not on the hub — so the alarm decision still happens locally in milliseconds. Ajax describes the chamber as having "blue and infrared LEDs that emit light at different wavelengths… allowing the detector to determine the size of volatile particles inside the chamber and respond only to smoke" (Ajax FireProtect 2 product page). That sizing step is what stops a kettle plume or a deodorant cloud waking the householder at 3 a.m.
How does HazeFlow 2 reduce false alarms?
HazeFlow 2 reduces false alarms in three layers: physical particle sizing, temporal pattern matching, and a confirmation pass before the radio packet leaves the detector.
Each layer addresses a real-world failure mode that has plagued optical detectors since the 1990s:
- Physical layer. Blue light scatters off small particles (combustion smoke, around 0.4 µm). Infrared scatters off larger particles (steam droplets, dust, cooking oil). Comparing the ratio tells the chamber what is actually drifting through it.
- Temporal layer. Real fire smoke builds up — a deodorant burst peaks then dissipates within seconds. HazeFlow 2 looks at how the optical signal changes over time and rejects single-shot transient events.
- Confirmation pass. Once the heuristic has flagged a candidate alarm, the firmware re-samples the chamber to confirm the pattern before the FireProtect 2 sounds and the Hub2 Plus or Fire Hub raises the system-wide alarm.
On UK domestic call-outs, the practical effect is simple: kitchens, hallways, lounges and bedrooms can run optical heads in places where you'd previously have had to drop down to a heat-only detector to keep the false-alarm rate acceptable.
Where does FireProtect 2 fit on a UK install?
FireProtect 2 sits in the wireless residential and small-commercial bracket: any site where the customer's compliance ceiling is BS 5839-6 (domestic) rather than BS 5839-1 (commercial life safety).
That covers the majority of Netview's Ajax installer base — HMOs up to Grade D1, single dwellings, light-commercial offices, holiday lets, and the residential overlay that sits inside a larger combined intruder-and-CCTV package. The detector is BSI Kitemark, UKCA and CPR certified, which is the badge set UK building control will accept for domestic fire under BS 5839-6 (Ajax BSI Kitemark announcement).
For commercial life safety on category L1, L2 or P sites — care homes, schools, hospitality, anywhere the FRA requires EN 54-2/4/13 certified equipment — you still spec the EN54 Fire Hub Jeweller with EN54 FireProtect (Smoke) and EN54 FireProtect (Heat) heads. Those are different SKUs, certified to a different standard, and they do not run HazeFlow 2 — they run an EN 54-7-compliant detection profile that's been third-party-tested. For background on that distinction see our complete Ajax EN54 installer guide.
FireProtect 2 placement: rooms to use, rooms to avoid
HazeFlow 2 makes optical FireProtect 2 viable in living spaces, hallways and bedrooms; it does not unlock bathrooms, hobs, garages or unheated outbuildings.
Ajax's own installation manual rules out installing FireProtect 2 in bathrooms, showers, or anywhere temperatures and humidity change rapidly — the algorithm is not designed for environments where steam is the baseline rather than the exception (FireProtect 2 (Heat/Smoke/CO) user manual). For those rooms, a heat-only or heat/CO variant from the FireProtect 2 line is the correct call.
Practical placement rules for the UK installer:
- Mount on the ceiling, in the centre of the room where possible.
- Keep at least 300 mm clear of light fittings, ceiling fans and air-conditioning vents.
- Avoid the apex of pitched ceilings — smoke layers below the apex.
- Do not fit within 1.5 m of a hob, oven, toaster or kettle station.
- For sleeping areas, BS 5839-6 requires a detector within 7.5 m of any habitable room door and on every storey.
Pairing FireProtect 2 with the right hub
FireProtect 2 talks Jeweller to a residential Ajax hub; for residential fire-and-intruder combined, that's typically the Hub2 Plus.
The Ajax Hub2 Plus Jeweller covers Ethernet, Wi-Fi and 2G/3G/LTE redundancy and supports up to 200 devices — which is plenty of headroom for the 8–15 fire detectors a typical Grade D1 or HMO install needs alongside intruder hardware. Ajax's Jeweller radio carries the alarm packet through several pairs of brick walls in real-world testing; for sites where the FireProtect 2 detector is more than 50 m of building fabric from the hub you add a ReX 2 to extend the radio.
If you're delivering a combined fire-and-intruder Ajax system on a residential job, the workflow we cover in Ajax fire alarm vs intruder alarm: UK compliance for combined systems stays valid — the FireProtect 2 line is the fire side of that pairing, the MotionProtect / DoorProtect range is the intruder side, and the hub does the brokering.
FireProtect 2 vs the EN54 FireProtect range
FireProtect 2 is the residential / EN 14604 algorithm; the EN54 FireProtect line is the commercial / EN 54-7 algorithm. They are not interchangeable on a Fire Risk Assessment.
Use the table below as a fast spec check on which line to quote on a job:
| Aspect | FireProtect 2 (residential) | EN54 FireProtect (commercial) |
|---|---|---|
| Standard | BS 5839-6, EN 14604, BSI Kitemark, UKCA, CPR | BS 5839-1, EN 54-2/4/7/13/23/25 |
| Detection algorithm | HazeFlow 2 (dual-spectrum optical, confirmation pass) | EN 54-7 third-party-tested optical / heat profile |
| Hub | Hub2 Plus Jeweller (residential) | EN54 Fire Hub Jeweller (10.1" CIE touchscreen) |
| Battery / power | 2 × CR123A or 2 × lithium (RB / SB / AC mains) | CR123A + Hub backup battery 24h or 72h |
| Sounder | Built-in 85 dB | Separate Sounder / Sounder+VAD SKUs (EN 54-3 / 54-23) |
| FRA category | D1, D2 (domestic / HMO) | L1, L2, L3, L4, L5, P1, P2, M (commercial / non-domestic) |
If the FRA on the job specifies any "L" or "P" category, default to the EN54 line: EN54 FireProtect (Smoke/Sounder), EN54 FireProtect (Heat/Sounder), EN54 FireProtect (Sounder/VAD), plus a red Manual Call Point at every final exit. We've documented that build-out in the Ajax Fire Hub Jeweller EN54 UK installer guide.
Common false-alarm triggers HazeFlow 2 ignores
HazeFlow 2's dual-wavelength sizing and pattern-matching are tuned for the eight transient sources that drive 80% of optical false alarms on UK residential sites.
- Cooking aerosols (toast, oil mist, frying steam) that drift into a hallway head.
- Aerosol products — deodorant, hairspray, polish, air-freshener.
- Steam from kettles, irons, showers escaping into a corridor.
- Cigarette and shisha smoke (still smoke, but a slow build that the temporal layer rejects unless density rises).
- Candle exhaust and incense.
- Dust from vacuuming, building work, plaster sanding.
- Cold-air condensation plumes near doors.
- Insect activity inside the chamber — the optical layout means a single small particle cannot fool both LEDs simultaneously.
It is still optical detection, so a real smouldering polyurethane sofa fire still trips it — just in seconds rather than minutes, because the confirmation pass uses the same chamber data the alarm decision was about to use anyway.
Range, retransmission and remote sites
FireProtect 2 talks Jeweller at up to 1,700 m line-of-sight; on a real building, plan for one ReX 2 or Fire ReX every 50 m of building fabric between the detector and the hub.
For Ajax-EN54 commercial installs, the dedicated EN54 Fire ReX is the certified retransmitter — the residential ReX 2 is not interchangeable on a BS 5839-1 install, even though the radio side is the same Jeweller protocol. We log this difference because we've seen it caught twice on FRA sign-off in the last year.
Compliance, certification and customer paperwork
FireProtect 2 carries BSI Kitemark plus UKCA marks — which means the customer-facing compliance certificate you hand over at the end of a domestic job lists the right approvals already; you don't need a separate route to BS 5839-6 sign-off.
For mixed sites — e.g. a flat above a shop — the rule of thumb is that any space the FRA categorises as commercial (the shop) drops onto the EN54 line, the residential side (the flat) can be FireProtect 2, and the two run on separate Ajax hubs because Ajax does not let an EN54 Fire Hub host residential FireProtect 2 detectors and vice versa. Customer-side, that's two apps on the customer phone (one for each hub) and two service contracts — flag this on the quote so the customer doesn't think the second hub is up-sell.
Site checklist: install for the lowest false-alarm rate
Even with HazeFlow 2 doing the heavy lifting, mounting choices still drive 60% of the false-alarm rate on a finished site. Run this checklist on every commission:
- Centre of ceiling, 300 mm clear of every air vent, light, fan and beam.
- Not within 1.5 m horizontally of a kitchen appliance — even if the room is technically a hallway.
- For open-plan kitchen-living rooms, run a heat-only FireProtect 2 over the kitchen area and an optical FireProtect 2 over the living area.
- Bathroom, en-suite, laundry, garage — heat-only or heat/CO, never optical.
- Lithium battery FireProtect 2 SB variants give 10-year battery; CR123A RB variants up to 7 years — flag the difference on hand-over so the customer schedules battery swaps correctly.
- Walk-test every detector once with the Ajax PRO Desktop test mode; smoke-spray the optical heads on first commission as a final sanity check.
FAQ
Can I use FireProtect 2 on a commercial site?
Only if the Fire Risk Assessment categorises that area as domestic (a residential flat, an HMO bedroom, a holiday let). Anything that needs BS 5839-1 / EN 54 sign-off uses the EN54 FireProtect line on the EN54 Fire Hub. The HazeFlow 2 algorithm is not what's certified — the EN 54-7 detection profile is.
How does HazeFlow 2 differ from the original HazeFlow?
The original HazeFlow ran on the first-generation FireProtect detector with a single optical channel; HazeFlow 2 adds the second LED wavelength and the temporal confirmation pass on top. In Ajax's own field data the false-alarm rate dropped substantially after the FireProtect 2 launch, which is why the FireProtect 2 is now the default Ajax residential head.
Does HazeFlow 2 also handle CO detection?
No — HazeFlow 2 is the smoke-detection algorithm only. The FireProtect 2 (Heat/Smoke/CO) and FireProtect 2 (CO) variants carry a separate electrochemical CO cell with its own threshold logic. Smoke and CO alarms are reported and acknowledged independently in the Ajax app.
What's the battery life on the lithium SB variant?
Up to 10 years on the FireProtect 2 SB line (sealed lithium, non-replaceable). The RB variants run on 2 × CR123A and last up to 7 years before the customer needs a battery swap. We recommend logging the install date in the Ajax app at commissioning so the renewal alert fires automatically.
Will HazeFlow 2 trigger on shisha or vaping aerosol?
Vape aerosol is borderline — the dual-spectrum sensor sees particles in the same size band as the lower edge of fire smoke. Heavy, repeated vaping inside an enclosed bedroom can still set FireProtect 2 off, which is the correct behaviour: you don't want a smoke detector that ignores combustion-like aerosol just because it happens to come from an e-cigarette.
Is there a mains-powered version?
Yes — the FireProtect 2 AC line is mains-powered with a battery backup, intended for installs where battery management is a customer pain point or where the local building control prefers permanently powered detectors. Same HazeFlow 2 algorithm, different power input.
Get the right Ajax fire SKU on your next quote
Netview is a Leicester-based UK distributor for Ajax wireless fire and intruder, and we hold stock of the full FireProtect 2 line plus every certified EN54 detector and accessory we've referenced above. If you'd like a same-day dispatch on the right hub-and-detector pairing for a job on your desk this week, call our trade team on 01163 800 838 or order direct from the FireProtect 2 RB (Heat/Smoke/CO) Jeweller product page.
Sources cited inline: Ajax FireProtect 2 (Heat/Smoke/CO) Jeweller product page; Ajax FireProtect 2 (Heat/Smoke/CO) Jeweller user manual; Ajax newsroom — FireProtect 2 BSI Kitemark certification announcement.
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