Construction, commissioning and live operations, UK wide
Data Centre Health and Safety
A data centre is a building that must never stop, maintained by people working next to energised equipment that in any other sector would be switched off first. AL23 Safety provides health and safety, fire safety and fire engineering support to operators, developers and fit out contractors across the UK.
Why it matters in data centres
The risks are real and so are the duties
Start with an honest statement. There is no dedicated HSE sector guidance for data centres and no Approved Code of Practice written for them. The regime is assembled from general law. The standard you are judged against is whatever a competent person would have done, decided after the incident rather than before it.
The defining control problem is uptime. Concurrent maintainability at Tier III and Tier IV assumes maintenance happens while the load stays live, which pushes people towards work on or near energised equipment. Regulation 14 of the Electricity at Work Regulations 1989 restricts exactly that, allowing live working only where it is unreasonable to work dead, reasonable to work live and suitable precautions are taken. A service level agreement is a commercial commitment. It is not by itself a reason why working dead is unreasonable. That tension is where most of the sector's serious electrical risk sits.
The main risks
Where the harm comes from
Arc flash and electrical energy
Switchrooms, UPS systems, static transfer switches and busbar carry fault energy capable of causing fatal burns, with the exposure highest during switching and maintenance.
Isolation failures in a live estate
Multiple supply paths, automatic transfer, stored energy in UPS batteries and capacitors mean that proving dead is far harder than opening one device.
Gas suppression discharge
Clean agent and inert gas systems can produce oxygen depletion, dangerous room over-pressurisation and extremely high noise levels in an occupied room.
Generator fuel and hydrogen
Bulk diesel, day tanks, fuel transfer and hydrogen evolution from lead acid battery rooms create explosive atmospheres that DSEAR requires you to zone and control.
Lithium-ion energy storage
Lithium UPS and on-site battery storage bring thermal runaway, flammable and toxic off-gassing and a fire that conventional suppression is not designed to stop.
Confined spaces and the construction interface
Chilled water tanks, fuel tanks, ductwork, sub-floor plenums and cable voids are confined spaces that on an expanding campus often sit metres from a live hall.
The regulations that apply
Your legal framework, in plain terms
The Health and Safety at Work etc. Act 1974 and the Management of Health and Safety at Work Regulations 1999 set the base duties. The Electricity at Work Regulations 1989 govern electrical work, supported by HSG85 on safe working practices, GS38 on test equipment and HSG230 on keeping switchgear safe. The Dangerous Substances and Explosive Atmospheres Regulations 2002 and ACOP L138 apply to battery rooms, bulk diesel storage, day tanks and fuel transfer. The Confined Spaces Regulations 1997 and ACOP L101 apply to tanks, plenums and voids. The Construction (Design and Management) Regulations 2015 govern build and fit out. The Regulatory Reform (Fire Safety) Order 2005 governs fire safety in occupation. Bulk oil storage also engages the Control of Pollution (Oil Storage) (England) Regulations 2001. Larger standby generator fleets can fall within the specified generator and medium combustion plant regime. Where the site holds 25 tonnes or more of dangerous substances, notification to the fire and rescue service is required under the Dangerous Substances (Notification and Marking of Sites) Regulations 1990.
Arc flash and the standard that does not exist
There is no UK arc flash regulation and no HSE endorsed calculation standard. Practice here draws on IEEE 1584 and NFPA 70E methods for incident energy calculation, on BS EN 61482 for arc rated clothing and on IET guidance. The legal hook remains regulation 4(4) and regulation 14 of the Electricity at Work Regulations 1989 together with the Personal Protective Equipment at Work Regulations. Anyone who tells you an arc flash study is a legal requirement in the UK is overstating it. What is required is that you understand the hazard, take suitable precautions and equip people properly. A calculated incident energy study is the most defensible way of showing that you did.
Fire safety in data centres
The life safety minimum is the floor, not the target
Data centres are not higher-risk buildings under the Building Safety Act 2022. The in-occupation duties for that regime do not apply. Approved Document B applies during construction and the Fire Safety Order applies in occupation. That gives you a life safety benchmark built around getting a small number of people out of a very large building. Almost every operator needs more than that, since the loss of a hall to smoke or to water is a business continuity event long before it is a life safety event. Our fire strategy work sets out both so the client can see which measures are law and which protect the asset and the contract.
Gas suppression deserves specific attention. Clean agent and inert gas systems are designed to BS ISO 14520 and BS EN 15004. The recurring risks are asphyxiation and oxygen depletion where a system discharges into an occupied room, over-pressurisation where relief venting has not been sized correctly, inadvertent discharge and lock off failures during maintenance. Nozzle noise on discharge is loud enough to damage spinning disks, which tells you something about the acoustic exposure for anyone in the room. Where people can be present at discharge, the peak values of 135 and 137 decibel C in the Control of Noise at Work Regulations 2005 matter alongside the oxygen depletion assessment. The weakest link is rarely the system design. It is the maintenance regime, where a contractor works in a protected room without the abort and lock off arrangements being applied and recorded.
Compartmentation is the other recurring finding. Cable penetrations between halls, plant rooms and risers are opened repeatedly through the life of the building and rarely reinstated to the standard of the original detail. Every containment route added after handover is a potential breach.
How we help
Built around your operation
We work across the lifecycle, from shell and core to a live campus taking additional halls into service while the existing ones carry load.
- CDM 2015 support for build, fit out and commissioning, including principal designer duties and the interface between live operations and contractor areas, through our CDM consultancy.
- Permit to work and isolation system design for LV and HV work, covering authorised persons, lock off hardware, proving dead and handback.
- Electrical safety audits against HSG85, GS38 and HSG230, including review of live working justifications against regulation 14.
- Arc flash risk reviews, covering incident energy assessment approach, boundary marking, PPE selection to BS EN 61482 and training.
- DSEAR assessments and zoning for battery rooms, bulk fuel, day tanks and fuel transfer, delivered through our DSEAR risk assessment service.
- Gas suppression safety reviews covering oxygen depletion, over-pressure relief, noise at discharge, signage, abort arrangements and maintenance lock off.
- Fire risk assessments, compartmentation surveys and detection reviews, written to serve both the legal duty and the continuity requirement.
Why AL23 Safety
Sector-aware support that gets used
Accountable
If your live working is being justified by the service level agreement rather than by engineering necessity, we write that down. That conversation is easier before an incident than after one.
Practical, not just compliant
A hall cannot be dropped for a convenient assessment. We plan around maintenance windows and change freezes rather than asking the operation to bend to us.
One team, three disciplines
Health and safety, fire safety and fire engineering in-house. The person reviewing the gas suppression risk to people sits with the person reviewing whether the system protects the asset.
Nationwide
We support data centre operators and their contractors across the UK, from single facilities to multi-building campuses.
Get in touch
Tell us the phase and we will tell you the priorities
Send us the site, the phase it is in and the maintenance model. We will tell you whether the pressing issue is the permit regime, the fire strategy or the construction interface.
Common questions
Answers, up front
Cannot see your question? Get in touch and we will answer it directly.
Contact usNo. There is no UK arc flash regulation and no HSE endorsed calculation standard. The duty comes from the Electricity at Work Regulations 1989, which require precautions to be suitable and people to be competent and properly equipped. A study based on recognised methods such as IEEE 1584, with arc rated PPE selected to BS EN 61482, is the clearest way to show you have met that duty.
No. The higher-risk definition covers buildings of at least 18 metres or 7 or more storeys containing two or more residential units. It was confirmed unchanged in the review published on 17 December 2025. Data centres fall outside it. Approved Document B applies to the building work and the Fire Safety Order applies in occupation.
It should not. The assessment has to prove what happens if it does. That means oxygen depletion modelling for the agent and room volume, correctly sized pressure relief venting, clear warning and abort arrangements plus a maintenance procedure that locks the system off before anyone works in the protected space. Discharge noise is also high enough to matter for the people present.
It depends on the phase and the number of buildings. A construction and fit out programme is normally scoped under CDM as project work. A live estate is better served by a retained arrangement so the permit system, fire strategy and contractor assurance stay current between audits. Our Core retainer starts at £250 per month, with ad hoc work at £95 per hour or £695 per day plus VAT.
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