BS 5839, BS 9251 and BS EN 12845, UK wide
Fire Detection and Suppression Design Reviews
Most fire alarm and sprinkler disputes are not installation failures. They are design decisions that nobody challenged. AL23 Safety reviews those decisions independently for clients across the UK.
What is a fire detection and suppression design review?
An independent check on what has been specified, before it is installed
This is a review and specification service. We do not install fire alarms, sprinklers or watermist systems and we do not sell equipment. We read the design, test it against the applicable standard and against your fire strategy, then tell you where it does not hold up.
That distinction matters commercially. When the party proposing the system is also the party pricing it, the category selection, the zoning and the sounder coverage tend to drift towards whatever is easiest to install. An independent review puts those choices back where they belong, which is with the fire strategy.
Who needs one
When a design has been assumed not derived
- New build and refurbishment projects where a contractor has proposed a fire alarm or suppression design that nobody independent has checked
- Buildings where the alarm category has been assumed rather than derived from the fire strategy
- Sites with a persistent false alarm problem that is eroding response and drawing fire and rescue service attention
- New care homes, where the Approved Document B amendment effective 2 March 2025 requires sprinklers throughout
- Higher-risk buildings preparing a Gateway 2 application, where the detection and suppression case has to be evidenced
- Residential blocks moving from stay put to simultaneous evacuation and needing a common fire alarm system
- Responsible persons whose fire risk assessment has flagged the alarm system as unsuitable
The regulations that apply
Your legal framework, in plain terms
The law does not name a British Standard. The Regulatory Reform (Fire Safety) Order 2005 requires the responsible person to provide appropriate fire detection and warning and, under article 17, to maintain fire safety measures in efficient working order. The Building Regulations 2010 set the functional requirement for new work through Part B. The British Standards are how you show that what you provided was appropriate, which is why a departure from them needs a written justification rather than a shrug.
BS 5839-1
Fire detection and fire alarm systems in non-domestic premises. It carries the category system, from M manual systems through L5 to L1 life protection and P1 and P2 property protection.
BS 5839-6
The equivalent code for domestic premises, using grades for the system type and categories LD1 to LD3 for the extent of coverage.
BS 9251
Fire sprinkler systems for domestic and residential occupancies, behind sprinklers in flats, houses in multiple occupation and care settings.
BS EN 12845
Automatic sprinkler systems for commercial and industrial installations, driving hazard classification, water supply duration and density of discharge.
Approved Document B
The 2025 amendment, effective 2 March 2025, requires sprinklers in all new care homes. It also removed BS 476-22 references for roof coverings and updated the regulation 38 fire safety information requirement.
What the service covers
Category through cause and effect to commissioning
- Alarm category selection under BS 5839-1, derived from the fire strategy and the evacuation strategy rather than from habit
- Domestic system grade and category selection under BS 5839-6, including the interface with a common system in mixed buildings
- Detection zoning, zone plan legibility and the search distance a responding person actually faces
- Detector type selection by location, including where optical, heat, multi-sensor or aspirating detection belongs and where each becomes a false alarm generator
- Audibility and voice alarm coverage, including sleeping risk provision and the case for visual alarm devices
- Cause and effect matrices written line by line so every input produces a defined output across alarms, doors, dampers, lifts, ventilation and shutdown signals
- False alarm reduction, covering detector siting near kitchens, bathrooms and plant, filtering and verification options and staff response protocols
- Sprinkler hazard classification, water supply adequacy, density and area of operation under BS EN 12845
- Residential and domestic sprinkler design under BS 9251, including tank and pump arrangements and the maintenance burden they create
- Watermist proposals, including whether the fire test evidence offered covers the hazard and occupancy in front of us
- Commissioning documentation review, including certification, as-fitted drawings and the logbook the responsible person inherits
Our process
Strategy first, then the design against the standard
- 01
Establish the strategy
We start with the fire strategy and the evacuation strategy. Detection and suppression decisions flow out of those. Reviewing a design without them is guesswork with a report attached.
- 02
Read the design against the standard
We check category, zoning, coverage, device selection and the supporting calculations against BS 5839, BS 9251 or BS EN 12845 as applicable.
- 03
Interrogate the cause and effect
We test the matrix line by line for gaps, conflicts and outputs that were never assigned an input. This is where most real defects are found.
- 04
Site verification
For occupied or partially built premises we verify the as-fitted position rather than accepting the drawing.
- 05
Report and support
We issue findings with a clear priority order, then support you through the contractor response and the resubmission.
What you get
A ranked verdict you can act on
- A design review report listing every finding, the clause it relates to and the action required, ranked by significance
- A marked-up cause and effect matrix showing what was missing, what conflicted and what we recommend
- A written category and zoning justification for building control, the fire and rescue service or an insurer
- A false alarm action plan where unwanted fire signals are the presenting problem, with owners and timescales
- A short verdict on whether the design is acceptable, acceptable with changes or not acceptable. We do not soften that.
What we need from you
The design package and the strategy behind it
- The fire strategy where one exists. Where it does not, an instruction to prepare one first
- The specialist contractor design package, including drawings, device schedules, calculations and the proposed cause and effect matrix
- Your current fire risk assessment and the alarm and sprinkler logbooks where the building is occupied
- False alarm records for the last twelve months where unwanted signals are the issue
- Access for verification where the system is already installed
Why AL23 Safety
Nothing to sell you at the end of it
We are reviewers, not installers
We have nothing to sell you at the end of the review, which is the only position from which a design opinion is worth reading.
The strategy comes first
Because fire strategy and fire engineering are in-house, the category we recommend is the category the escape strategy actually needs.
Accountable
When something is non-compliant, we say so clearly and set out the fix. We do not write findings that let a weak design through on a technicality.
UK wide
Manchester based, reviewing detection and suppression designs on projects across the UK.
Get a second opinion before you sign it off
Cheaper to argue on paper than at commissioning
Send us the design package and tell us what is bothering you. If it is sound we will say so quickly and you will have that in writing.
Common questions
Answers, up front
Cannot see your question? Get in touch and we will answer it directly.
Contact usNo. We review, specify and verify. We do not install, commission or maintain systems and we have no commercial relationship with equipment suppliers. If you need installation we will help you write the specification and evaluate the tenders, then check what gets delivered against what was promised.
Yes for new build. The Approved Document B amendment effective 2 March 2025 requires sprinklers in all new care homes in England. It does not retrospectively require them in existing care homes, although an existing home may still reach that conclusion through its own fire risk assessment or through a material alteration. We look at both positions rather than only the easy one.
It comes from the fire strategy, the evacuation strategy and the risk to occupants, not from a preference. A building relying on simultaneous evacuation of sleeping occupants needs a different answer from a single storey office with immediate detection at the point of risk. We write the justification down so the choice survives scrutiny by building control, an insurer or an enforcing officer.
Often, yes. Most unwanted fire signals trace back to detector siting, detector type, a matrix that escalates too aggressively or a staff protocol that does not allow investigation. We look at the pattern in your records first. Be aware that the fix is sometimes managerial rather than technical. No specification change will substitute for that.
Cost depends on the size of the building, the number of systems in scope, whether site verification is needed and whether we are reviewing one package or a whole development. Cause and effect interrogation on a complex building takes longer than a category check on a small one. We quote a fixed fee once we have seen the package.
Yes. The critical question with watermist is whether the fire test evidence supporting the system covers your actual hazard, occupancy and ceiling height. Watermist is not a general substitute for a sprinkler system. We will tell you plainly where the evidence offered does not stretch to your building.
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