23% and rising: why lithium-ion battery fire is now a workplace problem

It's gone 11pm at a self-storage facility, motion-sensor lighting clicking off unit by unit as the last visitor leaves. Somewhere inside one of those units, a customer's forgotten e-bike battery is quietly overheating. Nobody's there to smell it. Nobody's there to see the vapour building in the dark. By the time a corridor sensor picks up smoke, the fire is already spreading cell to cell - faster than a response built around smoke alone can catch up with.

For years, the lithium-ion battery fire story has belonged to somebody else's house. Domestic e-bikes charging overnight in hallways. E-scooters left by the front door. That framing isn't wrong. It's just incomplete and increasingly out of date.

UK fire brigades attended lithium-ion battery fires at a rate of 4.8 a day in 2025 - nearly 1,760 incidents, up 147% since 2022 (QBE European Operations, FOI research, 11 May 2026). QBE's own analysis of that data splits the incidents by location: 46% in homes, 31% outdoors and 23% in commercial premises. That means more than half of these fires now happen somewhere other than a home. And getting on for a quarter happen on premises that a business, not a homeowner, is legally responsible for. The commercial figure comes from a single insurer's FOI analysis, not official Home Office statistics. Treat it as the strongest available indicator, rather than a definitive market-wide number. Even read conservatively, a 147% rise in attended fires over three years puts commercial premises inside a fast-growing risk category, not a footnote to one.

In London alone, the Fire Brigade attended 521 lithium-ion battery fire incidents in 2025 - up 28% year-on-year - resulting in 109 injuries and three deaths (London Assembly Research Unit, 6 March 2026). This is no longer a niche domestic hazard. It's a workplace problem - and one that needs the same forward planning as your Fire Alarm servicing contract already gets.

In practical terms: a lithium-ion fire begins when a battery cell overheats, is damaged or short-circuits until it can no longer shed heat fast enough - tipping into thermal runaway, a self-sustaining chain reaction that behaves differently from a conventional fire and is correspondingly harder to detect, contain and extinguish. That difference is what the rest of this article explains.

The Big Picture

• The domestic framing is out of date. QBE's FOI data shows 23% of UK lithium-ion battery fires now happen on commercial premises, sitting inside a total that has grown 147% in three years - this is a workplace risk, not just a household one.
• These fires behave differently from the fires your systems were designed around. A failing lithium-ion cell goes through a process called thermal runaway and it gives off an early warning sign - off-gassing - that conventional smoke detection often misses or catches too late.
• Certain commercial sectors carry disproportionate exposure. Logistics depots, waste and recycling sites and self-storage facilities all combine high battery density with limited supervision – the kind of combination that can turn a single failing cell into a serious loss.
• Insurers are already pricing this risk. Aviva's own survey found only 15% of UK organisations had carried out a Fire Risk Assessment specifically covering lithium-ion batteries, even as claims for these fires rise year on year - a compliance gap insurers are actively pricing.
• Detector selection now has a live standard to answer to. BS 5839-1:2025, current since April 2025, sets out how detector choice should be justified for premises with elevated battery-fire risk - and detector choice specifically for battery risk is something most commercial guidance on this topic hasn't yet worked through in detail.

What's actually happening inside a failing battery

A lithium-ion cell packs a lot of energy into a small space, sitting right next to a flammable liquid electrolyte. Damage, overcharging, overheating or a manufacturing defect can push a cell into generating more heat than it can shed. Past a certain point, the reaction becomes self-sustaining. That's thermal runaway. Each failing cell heats its neighbours in turn and the fire cascades cell to cell through the pack.

Before flames appear, a failing cell usually off-gasses. It vents a cloud of flammable, toxic vapour - electrolyte solvents mixed with hydrogen. This is the earliest reliable warning sign of a battery in trouble, often minutes before visible fire. It's also the signal that conventional point smoke detection was never designed to catch in time.

The fire that follows is chemically driven. It generates its own oxygen supply, which is why smothering agents and conventional firefighting methods struggle against it. It burns hotter and faster than an ordinary fire. And it can look extinguished, then reignite hours or days later, because heat is still propagating somewhere inside the pack.

"Thermal runaway caused by these types of batteries burns differently, takes much longer to tackle and can require up to 10 times more water to contain."
Adrian Simmonds, Risk Manager, QBE Insurance (QBE press release, 11 May 2026)

That difference - in behaviour, not just in scale - is why early detection matters more for lithium-ion risk than for almost any other fire type a Responsible Person has to plan around.

Why this is now a commercial premises problem, not just a home one

Three sectors stand out for the strength of the evidence behind them.

Logistics and last-mile depots run high-density overnight charging for e-cargo bike and van fleets, often unattended for hours at a stretch. Dozens of packs charging simultaneously, out of sight, is precisely the scenario thermal runaway thrives in.

Waste and recycling sites face a different version of the same problem: batteries hidden inside discarded electricals, crushed or damaged during collection and processing, igniting bulk combustible waste around them. Battery-related fires in refuse vehicles and waste facilities exceeded 1,200 in 2023/24, a 71% year-on-year rise from around 700 the year before (Environmental Services Association and Material Focus). Those incident counts are underpinned by reported data, though the widely cited £1 billion-a-year cost figure attached to them is a modelled industry estimate rather than an audited one, produced by trade bodies with a clear policy interest in the issue.

Self-storage carries a harder problem still: unknown contents. Operators frequently have no reliable way of knowing whether a unit contains an e-bike, a stack of power banks or nothing of concern at all - until something goes wrong.

Aviva recorded a 7% year-on-year rise in customer claims for lithium-ion battery fires and a separate Aviva business survey found that only 15% of UK organisations had carried out a workplace Fire Risk Assessment specifically covering lithium-ion batteries. Both figures come from Aviva's own claims book and survey panel rather than a national census, but they line up with the wider claims trend reported across the insurance sector - and they point to a stark compliance gap: the large majority of UK businesses haven't yet assessed a risk their own insurers are actively pricing for.

Allianz UK's claims data adds further scale, drawn from two separate releases. Its residential claims data puts the average lithium battery fire claim at £50,000, while a separate motor-trade release puts two commercial losses at £5 million and £1.5 million, both attributed to stored EV batteries.

Insurers are, in other words, several steps ahead of most Responsible Persons on this - the Regulatory Reform (Fire Safety) Order 2005 (FSO 2005)'s term for whoever has control of a premises in connection with a trade, business or other undertaking, typically the employer or building owner. That gap between what's assumed and what's actually in place doesn't close on its own and it's the Responsible Person, not the insurer, who carries the risk in the meantime. That's where a BS 5839-1:2025-compliant detection strategy comes in - it's the practical bridge between what insurers are already assuming you've done and what most premises have actually done.

What BS 5839-1:2025-compliant detection actually looks like for battery risk

BS 5839-1:2025 (the British Standard governing Fire Detection and alarm system design in non-domestic premises) is a code of practice, not law. It's voluntary - the legal duty sits with FSO 2005. But Approved Document B references BS 5839-1:2025 directly, which is why it is widely treated in practice as the benchmark of good practice for Fire Detection design. The 2025 edition, published 30 April 2025, replaced BS 5839-1:2017+A2:2024 and it sets out eight system categories - M, L1 to L5, P1 to P2 - with the appropriate category for a given space determined by Fire Risk Assessment, not guesswork.

For battery risk specifically, the detector-selection depth matters. A single-point smoke detector, positioned for a conventional fire, is a poor match for a threat that announces itself first as off-gassed vapour rather than smoke. No single detector technology is likely to solve this on its own. A properly justified BS 5839-1:2025 strategy for a charging area or battery storage room typically draws on a combination of technologies: multi-sensor detectors, which combine smoke, heat and CO (carbon monoxide) sensing to detect faster and with fewer false alarms; and aspirating smoke detection (ASD), which samples air continuously through pipework and can pick up very early smoke in high-value stores or warehousing. ASD systems are tested to BS EN 54-20, which grades sensitivity into three classes - Class A for very early warning, through to Class C for general Fire Protection - so the class specified should match how early a warning the space actually needs.

Off-gas and VOC (volatile organic compound) detection deserves a specific caveat here. It's a genuinely strong technology for early warning - detecting electrolyte vapour and hydrogen at the point a cell first vents, potentially minutes ahead of any smoke. But it is not a BS 5839-1:2025 primary detector. We're not aware of any dedicated UK detection standard governing it yet. The honest way to specify it is as a supplement to a compliant detection design, integrated alongside conventional and multi-sensor detection - not as a replacement for it.

Design, installation, commissioning and maintenance of a system like this to BS 5839-1:2025 sits within the scope of BAFE SP203-1, the scheme covering Fire Detection and alarm work, with certification bodies including NSI, SSAIB, BSI and NICEIC. BAFE registers companies, not individuals - the correct term is "BAFE SP203-1 Registered", not that an individual engineer "is BAFE registered". Like BS 5839-1:2025 itself, SP203-1 registration is voluntary, not a legal requirement. The legal duty sits with FSO 2005 instead, and it comes down to three things: you need a suitable and sufficient Fire Risk Assessment (Article 9), general fire precautions in place (Article 8), and your fire safety facilities and equipment kept in efficient working order (Article 17). FSO 2005 is outcome-based. It doesn't name BS 5839-1:2025 or specify testing frequencies - but non-compliance that places people at risk of death or serious injury, as enforced by the local Fire and Rescue Authority, carries an unlimited fine and up to two years' imprisonment.

Why the extinguisher-in-the-corner isn't the answer

FSO 2005 requires "appropriate fire-fighting equipment" on premises, but it never mandates portable extinguishers by name. That distinction matters, because extinguisher marketing around lithium-ion risk has run well ahead of the evidence.

Start with a basic point of accuracy: lithium-ion battery fires are not Class D. Class D covers combustible metals - magnesium, sodium, titanium - not lithium cells and treating them as equivalent is a genuine misclassification, not a technicality. Industry sources report that BS ISO 3941:2026 introduces a new Class L classification for lithium-ion battery fires - but that's a classification, not a performance rating. There is currently no BS EN 3 performance rating for extinguishers against lithium-ion fires, so any claim that a product is "Class L rated" for extinguishing performance isn't backed by a recognised UK test. The rationale for a distinct class mirrors the mechanism explained earlier: lithium-ion fires exhibit the faster heat release and cell-to-cell fire growth of thermal runaway, behaviour the existing extinguisher classes (A, B, C, D, F) were never designed to describe – which helps explain why a new class has been introduced, even without a matching performance rating yet.

The trade body guidance is blunt about the limits. The FIA's "Guidance on Li-Ion Battery Fires" (December 2020) states plainly that "complete extinguishment may not be possible" with portable extinguishers. Chubb Fire & Security UK has warned that portable fire extinguishers will not extinguish a lithium-ion battery fire in anything larger than an e-scooter and will certainly not extinguish an Electric Vehicle (EV).

Sprinklers, where fitted to the commercial anchor standard BS EN 12845:2015+A2:2026, have a genuine role - they cool and control fire spread, buying critical time. But they don't "extinguish" a battery pack in thermal runaway either; a burning cell keeps generating its own heat and oxygen internally, regardless of what's applied from outside. The honest position for any Responsible Person to work from is that fire-fighting equipment and suppression systems reduce risk and slow spread - they don't guarantee an outcome and we won't tell you otherwise.

What a Responsible Person should actually do next

None of this is a one-off fix. A detection strategy that's compliant on day one drifts out of alignment as charging habits change, device numbers grow and sensors age - which is why the maintenance relationship matters as much as the initial install. A detector justified for last year's charging pattern won't necessarily catch next year's failure.

BS 5839-1:2025 calls for twice-yearly inspection and testing of Fire Detection and alarm systems, on top of weekly user checks. Off-gas and VOC sensors carry their own servicing profile: some modern units run largely calibration-free with long service lives, while older electrochemical sensors typically need calibration and replacement on a two-to-five-year cycle and catalytic or infrared sensors sit somewhere between the two. None of these figures are fixed - always check the specific manufacturer's servicing schedule rather than assuming a single interval applies across every sensor type.

Practically, that means the sensible next step isn't a one-off purchase. It's a short review of your current detection strategy against BS 5839-1:2025 - we can identify where conventional point detection alone leaves a gap in charging or storage areas, and then keep that strategy current through a recurring servicing and calibration arrangement, rather than leaving it to drift for another five years. Get that right and the next failing cell announces itself as off-gas at 11pm - not as smoke in a corridor after the fact.

Before You Go

• Stop treating this as a domestic story. QBE's data puts 23% of lithium-ion fires on commercial premises, inside a total up 147% since 2022 - it belongs on your risk register, not someone else's.
• Off-gassing, not smoke, is the earliest signal. If your detection strategy relies solely on conventional point smoke detectors in charging or storage areas, it's likely picking up the problem later than it needs to.
• Check where you sit against BS 5839-1:2025. It's voluntary, but it's the recognised benchmark referenced by Approved Document B - and it's the standard your insurer is likely to expect you've considered.
• Don't rely on an extinguisher to solve this. Even the industry's own guidance is clear that complete extinguishment of a lithium-ion fire may not be achievable with portable equipment - plan for early detection and containment instead.
• Build in the maintenance relationship from the start. A BS 5839-1:2025-compliant detection strategy only stays effective with twice-yearly servicing and properly calibrated sensors - we can run a short review of your detection strategy against BS 5839-1:2025 and flag where point smoke detection alone leaves a gap. If you haven't had that review yet, contact us and we'll book it in before your next servicing date, not after an incident forces the question.

Frequently Asked Questions

Is BS 5839-1:2025 a legal requirement for detecting lithium-ion battery fires?

No. BS 5839-1:2025, the British Standard covering Fire Detection and alarm system design in non-domestic premises, is a voluntary code of practice, not a legal requirement in itself. Your legal duty sits with the Regulatory Reform (Fire Safety) Order 2005, which requires a suitable and sufficient Fire Risk Assessment (Article 9), general fire precautions (Article 8) and maintained Fire Safety equipment (Article 17). Non-compliance that puts people at risk of death or serious injury carries an unlimited fine and up to two years' imprisonment. In practice, though, BS 5839-1:2025 functions as the recognised benchmark because Approved Document B references it directly and it's the standard your insurer is likely to expect you've already considered.

Why doesn't a standard smoke detector catch a lithium-ion battery fire early enough?

Because it's designed to catch smoke and a failing cell gives off a different warning sign first. Before flames appear, a cell in trouble typically off-gasses - venting a cloud of flammable, toxic vapour made up of electrolyte solvents and hydrogen, often minutes before any visible fire. Conventional point smoke detectors weren't designed to catch that early enough. A properly justified BS 5839-1:2025 strategy for a charging or storage area typically combines multi-sensor detectors (smoke, heat and carbon monoxide) with aspirating smoke detection for continuous early sampling. Off-gas and VOC detection is a genuinely strong supplementary technology, but it isn't yet a BS 5839-1:2025 primary detector - there's no dedicated UK detection standard governing it, so it should sit alongside compliant detection, not replace it.

Can I rely on a Fire Extinguisher to put out a lithium-ion battery fire?

Not on its own and not reliably. Lithium-ion battery fires aren't Class D - that classification covers combustible metals such as magnesium and titanium, not lithium cells. Industry sources report that BS ISO 3941:2026 introduces a new Class L classification for lithium-ion fires, but that's a classification, not a performance rating - there's currently no BS EN 3 performance rating for extinguishers against lithium-ion fires. The FIA's own December 2020 guidance states plainly that "complete extinguishment may not be possible" with portable extinguishers and manufacturer guidance goes further, warning that portables won't extinguish anything larger than an e-scooter. Sprinklers, where fitted to BS EN 12845, cool and control fire spread rather than extinguish a pack in thermal runaway. Plan around early detection and containment, not guaranteed extinguishment.

Which commercial sectors are most at risk from lithium-ion battery fires?

Three sectors stand out in the evidence. Logistics and last-mile depots run high-density overnight charging for e-cargo bike and van fleets, often unattended for hours at a stretch. Waste and recycling sites face batteries hidden inside discarded electricals that get crushed or damaged during collection and processing - battery-related fires in refuse vehicles and waste facilities exceeded 1,200 in 2023/24, a 71% year-on-year rise (Environmental Services Association and Material Focus), though the widely cited £1 billion annual cost figure attached to that is a modelled industry estimate, not an audited one. Self-storage carries a harder problem again: operators often have no reliable way of knowing what's in a unit - an e-bike, a stack of power banks or nothing of concern - until something goes wrong.

How often does a lithium-ion detection strategy need to be serviced?

BS 5839-1:2025 calls for twice-yearly inspection and testing of Fire Detection and alarm systems, on top of weekly user checks. Off-gas and VOC sensors, where fitted, carry their own servicing profile: some modern units run largely calibration-free with long service lives, older electrochemical sensors typically need calibration and replacement on a two-to-five-year cycle and catalytic or infrared sensors sit somewhere between the two - always check the specific manufacturer's schedule rather than assuming one interval fits every sensor type. None of this is a one-off fix. A strategy that's compliant on day one drifts as charging habits change and device numbers grow, which is why a recurring servicing and calibration arrangement with us matters as much as the initial installation.

Is lithium-ion battery fire risk really a commercial problem or mainly a domestic one?

Commercial premises now account for a meaningful and fast-growing share. QBE's FOI research found UK fire brigades attended lithium-ion battery fires at a rate of 4.8 a day in 2025 - around 1,760 incidents, up 147% since 2022 - with 23% of those happening on commercial premises, against 46% in homes and 31% outdoors. That commercial figure comes from a single insurer's FOI analysis rather than official Home Office statistics, so treat it as the strongest available indicator rather than a definitive market-wide number. Even read conservatively, a 147% rise in three years puts commercial premises inside a fast-growing risk category. In London alone, the Fire Brigade attended 521 such incidents in 2025, up 28% year-on-year, resulting in 109 injuries and three deaths.