Lithium-ion battery fires: what to do, and why there is no Class L extinguisher

Ask what class of fire a lithium-ion battery makes and a good share of the UK results will answer Class D, the metals class. The British standard that governs how you choose extinguishers says the opposite, in as many words. The commentary to clause 7.5 of BS 5306-8:2023 reads: “Disposable primary lithium metal batteries contain flammable metallic lithium and are therefore class D hazards. Rechargeable lithium-ion batteries contain lithium salts, not metallic lithium. As such they are not Class D hazards.”

That distinction decides which extinguisher is wrong, and there is a second one behind it. In January 2026 a genuinely new class of fire arrived, the first since Class F was added by amendment in 2004. It does not mean what the headlines suggest.

The quick answer

What is actually happening inside the battery

The failure mode has a name, thermal runaway, and the Fire Industry Association defines it as an “exothermic chemical reaction generating more heat than is being dissipated”, characterised by a self-heating rate of 10°C per minute or greater. That is a rate of temperature rise rather than a temperature.

One temperature is worth knowing, and worth labelling properly. Research commissioned by the Office for Product Safety and Standards and carried out by WMG at the University of Warwick: “To reach thermal runaway, some part of a cell must reach an abnormally high temperature of around 150-180 °C.” That is the local cell temperature needed to start the reaction. It is not a flash point, not an auto-ignition temperature and not how hot the fire burns.

Once it starts, the same government-commissioned research says it “proceeds rapidly and is almost impossible to halt with any amount of cooling”, and that it “invariably starts in a single cell and can propagate to other cells”. The FIA sets out the sequence in six stages: temperature increase, venting and gassing off, flare, steady burn, flash fireball, explosion.

The vented gas is “predominately H2, CO2, CO, Hydrocarbon gases and battery electrolyte solvents” in the FIA’s description, and the build-up “may present an explosion hazard”. It is also easy to misread: the Faraday Institution describes “a white vapour cloud that may be mistaken for smoke or steam”, and records emergency services having made exactly that mistake.

The fire is also not waiting for your oxygen. In advanced propagation the FIA states “The fire is also not dependent on an oxygen supply”, which is why smothering agents can fail on it. Nor is it necessarily over when it looks over. Writing about electric vehicle batteries, the Faraday Institution says they “have the potential to reignite hours, days or even weeks after they have been extinguished, and may do so more than once”.

Class D, Class L, and what neither of them buys you

BS EN 2, the standard behind UK extinguisher marking, gives five classes: A for solids, B for liquids or liquefiable solids, C for gases, D for metals, F for cooking oils and fats in cooking appliances. There is no Class E, because the classes describe the fuel and electricity is not a fuel.

Class L is real and it is new. BS ISO 3941:2026 was published on 31 January 2026, replacing the 2007 edition, and adds Class L for lithium-ion cells and batteries where no metallic lithium is present. The definition turns on the absence of lithium metal, which is the same reason these fires are not Class D.

The part the coverage skips is what that does not do. BS ISO 3941 classifies fires; it does not certify equipment. Class L has not been added to BS EN 2 or to the BS EN 3 rating system, so no portable extinguisher carries a Class L rating. That is narrower than saying nothing has been tested on lithium, and the difference matters when you are reading a product page. The route to a letter rating is BS EN 3-11, which BSI still listed at Approval stage and unpublished in late August 2026.

Its 2025 enquiry draft is candid about the limits: “As of yet, there are no known extinguishing agents that can stop a thermal runaway in a lithium-ion battery cell. There are, however, extinguishing agents that can effectively stop the fire propagation in the battery pack.” When it lands it will be scale-limited, covering phones, laptops, power tools, drones and bicycles, and expressly not vehicle batteries or stationary storage.

So what are the lithium extinguishers on sale tested against? Usually NTA 8133, a Dutch technical agreement published by NEN in November 2021 and updated in 2025, scoped to batteries up to 600 Wh. It is a real test with a real rig, and it is not a British or European standard, so a product can hold genuine lithium test evidence and still have no Class L rating. Check the Kitemark and you find ordinary ratings underneath: the BSI product directory entry for one AVD range (licence KM 794246, revised 27 November 2025) shows an EN 3 Kitemark carrying 5A and 13A ratings. Those are Class A wood-crib ratings.

Can you put one out?

The honest answer is the one the British standard gives: “It is likely that a lithium-ion battery will burn out rather than be extinguished.”

What BS 5306-8:2023 recommends, at clause 7.8, is cooling: “For lithium-ion batteries, water or water-based extinguishers should be provided to cool individual small rechargeable devices that are no longer on charge.” Read that as what it is. It is a code of practice telling a responsible person what to put on the wall, not an instruction to an occupant to stay and fight. It does kill the flat “never use water” rule that circulates online, subject to two conditions doing a lot of work.

The first is scope: “This subclause covers only lithium-ion batteries in individual small rechargeable devices (such as laptops, mobile phones, e-cigarettes and portable power tools). It does not cover multiple devices or lithium-ion batteries in larger devices.” A phone on a desk is in scope. An e-bike in a corridor is not.

The second is the charging cable. Clause 7.7.1 recommends that “only electrically non-conductive extinguishing media, such as non-conductive powder, carbon dioxide or clean agent” should be used on live electrical equipment, which would rule water out. The standard resolves it by carving these devices out: “For the purposes of this document, lithium-ion batteries in individual small rechargeable devices are not considered to be live electrical equipment (see 7.7).” A device still plugged in “needs to be disconnected/isolated before any attempt is made to cool it”.

Carbon dioxide is not the answer here. It may knock down flame around the device, but it does not deliver the sustained cooling needed to slow propagation, and cooling is the mechanism the standard is relying on. The FIA is equally direct on the other misfire: “As these are not metal fires, class D powders such as L2 (for lithium metal fires), are not suitable for lithium-ion battery fires”, and powder “does not have any cooling properties”.

None of which changes the instruction to the person who finds one, which is the next section and is the same for everybody.

What the fire service tells your staff to do

The fire services that have published on this say the same thing, and it is shorter than any of the above. The National Fire Chiefs Council: “In the event of an e-bike, e-scooter or lithium-ion battery fire, do not attempt to extinguish the fire. Get out, stay out, call 999.”

London Fire Brigade’s ChargeSafe guidance is the same instruction with the steps spelled out: “If a battery begins to smoke or catches fire: get out immediately, raise the alarm, call 999, do not attempt to tackle the fire yourself.” West Yorkshire adds the detail people forget under pressure, to close doors behind you as you leave, if it is safe to do so. Essex, writing for businesses in May 2025, adds the one that matters most: “Do not move or touch a smoking, swollen, or damaged battery. Call 999 and inform the operator about the potential involvement of lithium-ion batteries.”

That is stronger than the general UK line. The Home Office risk assessment guides say people with no training “should not be expected to attempt to extinguish a fire”. For lithium-ion it is not a matter of expectation. It is do not.

The warning signs matter more than the extinguisher

Many of these fires announce themselves first, and that is the stage where staff can change the outcome. Not all of them do: the OPSS-commissioned research is clear that a cell can fail with no outward indication, so a warning-sign checklist is a bonus rather than a plan.

London Fire Brigade lists a battery that becomes “extremely hot to the touch”, one that “appears swollen or misshapen”, lumps, leaking, damage to the casing, and hissing or cracking sounds. The Scottish Fire and Rescue Service adds smoke, an unusual smell, and one the others tend to leave out: a device “taking longer to charge or does not fully charge”.

The Scottish instruction at that point is four words long. “Don’t use or charge your device.” Do not pick it up to prove it is fine. Essex County Fire and Rescue Service, writing for businesses, is explicit that a battery already smoking, swollen or damaged should not be moved or touched at all: cut the power at the socket if you can do that without going near it, keep people away, and get it collected for proper disposal. A swollen battery in a bin bag is tomorrow’s fire somewhere else.

What the law actually asks of you

There is no statute requiring a lithium extinguisher and no lithium clause to comply with. There is a duty that already covers it.

In England and Wales, article 9(1) of the Regulatory Reform (Fire Safety) Order 2005 requires the responsible person to make “a suitable and sufficient assessment of the risks to which relevant persons are exposed”. Article 9(3) requires that assessment to be reviewed if “there has been a significant change in the matters to which it relates”. Department for Transport guidance from 1 February 2024 joins the dots for you: “The potential introduction of a new fire hazard would require a review of the fire risk assessment.” A rack of delivery-rider batteries charging in the back corridor is a new fire hazard.

The Order does not extend to Scotland or Northern Ireland. Scotland runs on Part 3 of the Fire (Scotland) Act 2005, where section 53 carries the employer duty to employees and section 54 reaches owners and others responsible for premises, with detail in the Fire Safety (Scotland) Regulations 2006. Northern Ireland has its own regime under the Fire and Rescue Services (Northern Ireland) Order 2006 and the Fire Safety Regulations (Northern Ireland) 2010. The assessment duty is the common thread; the article numbers are not.

Article 13 covers equipment, and it names no product. Premises must be equipped with “appropriate fire-fighting equipment” where necessary to safeguard relevant persons, and only to the extent that it is appropriate, judged against the dimensions and use of the premises and what is kept in them. So no statute prescribes a lithium-branded product. What a salesperson cannot tell you is whether your assessment needs one, because that conclusion is yours to reach and, once reached, you have to act on it.

Then there is the gap. The Home Office fire risk assessment guides issued under article 50, the documents a responsible person is formally pointed at, contain no lithium-ion content whatsoever. A full-text search of the sleeping accommodation, offices and shops, and residential care guides returns nothing for lithium, e-bikes, e-scooters, mobility scooters or battery charging. All three were last updated in September 2023. The official guide is not going to tell you what to do here.

The most recent workplace-specific guidance arrived in January 2026, when the Crown Premises’ Fire Safety Inspectorate published guidance on e-bikes in the workplace. It is written for the Crown premises that body regulates rather than for every employer, which is worth knowing before you cite it, and it is still the clearest statement available: run an assessment that “explicitly considers the risks posed by e-bikes and lithium-ion batteries”. It also makes a point most battery advice misses, that article 23 of the Fire Safety Order puts a duty on employees too, to take reasonable care and cooperate.

Where this bites in your building

Care homes. Mobility scooters and powered wheelchairs are the exposure, and that guidance predates the e-bike panic. The Scottish Government’s specialised housing guidance from February 2022: “The charging of scooters in dead end corridors and single stairway escape routes should not be permitted in any circumstances.” The NFCC’s mobility scooter guidance recommends in-building storage of at least 30 minutes’ fire resisting construction with detection. A 2025 report for the Building Safety Regulator noted at 4.4.6 that Approved Document B “does not provide any guidance on the use, charging and storage of mobility scooters within buildings”, so the risk assessment is carrying this alone. Staff in residential settings should also work through risk assessing in adult residential settings.

Takeaways, cafes and restaurants with delivery. London Fire Brigade’s fire safety page for food businesses says it directly: “If you provide delivery service, you should make sure you follow our advice for charging and storing e-bikes.” The risk is concentrated rather than general. Of 170 e-bike fires notified to the Office for Product Safety and Standards in 2024, on a voluntary scheme OPSS says “cannot be used to estimate incidents at a national level”, 77 involved post-market conversion kits. DfT guidance names the group outright, recording that LFB “has identified ‘gig economy’ delivery riders as a particularly high-risk user group, due to widespread use of owner-modified e-cycles”. A self-employed rider is still a relevant person under the Order, so the control is a house rule about where charging happens, not staff discipline.

Hotels and pubs with rooms. Guests arrive with e-bikes, scooters and chargers, and the sleeping-accommodation guide says nothing about any of it. A charging policy that keeps batteries out of bedrooms and corridors is a decision someone has to make and write down.

Kitchens, and the bin. Cordless equipment, power banks and vapes all end up in general waste. Material Focus, with the NFCC, estimated more than 1,200 battery fires in UK bin lorries and waste sites in a year, up from around 700 in 2022. Both figures are extrapolations from partial local-authority returns rather than counts. Since 1 June 2025 it has been illegal for a business to sell or supply single-use vapes, and any leftover stock has to be separated and recycled rather than binned.

Warehousing and food manufacturing. Forklift and pallet-truck charging bays, where the sector knows it is behind: the UK Warehousing Association said in January 2026 that “many warehouse operators remain uncertain about what constitutes best practice”, and HSE’s guidance on charging areas, INDG139, is built around lead-acid chemistry rather than lithium-ion.

How common is this, really

Enough to plan for, with caveats. Insurer QBE put a freedom of information request to all 49 UK fire services in February 2026; 42 replied. Their answers give 4.8 lithium-ion battery fires a day across the UK in 2025, about one every five hours, a 147% rise over three years, and 23% of them at commercial properties.

A separate Press Association request to the same 49 services got 37 replies and a different e-bike total for the same year, 432 against QBE’s 520. The two are not directly comparable: different brigades answered, and the responses are not a national count because no mandatory one exists.

For rough scale, fire services in England attended 142,494 fires in the year to March 2025. That is England and a financial year against UK-wide calendar-year FOI returns, so it will not divide cleanly, but the order of magnitude holds: lithium-ion fires are a small share of all fires. They get attention for the growth rate and the way the fire behaves, not the count. London Fire Brigade attended 206 e-bike and e-scooter fires in 2025, its highest annual total: one every two days.

You will also see a statistic claiming 71% of organisations have not updated their fire risk assessments for lithium-ion. We could not find a primary publisher for the survey behind it, and the article carrying it was written by an employee of an extinguisher manufacturer. Treat it as marketing.

Frequently asked questions

What class of fire is a lithium-ion battery?

Under BS ISO 3941:2026 it is Class L, a classification added on 31 January 2026 for lithium-ion cells and batteries containing no metallic lithium. It is not Class D, which is burning metal, and it is not Class E, which does not exist in the UK. Class L does not appear in BS EN 2 or in extinguisher ratings.

Can you use water on a lithium battery fire?

BS 5306-8:2023 clause 7.8 recommends providing water or water-based extinguishers to cool an individual small rechargeable device that is no longer on charge, and treats those devices as not being live electrical equipment. That is guidance on what a premises should stock. It is not an instruction to occupants: UK fire services tell anyone who sees a battery smoking or burning to get out, stay out and call 999, and for an e-bike, a mobility scooter or anything larger that is the only answer.

Is there a Class L fire extinguisher?

No. Class L classifies the fire, not the equipment. BS EN 3-11, the standard that would create a lithium-ion extinguisher rating, was still at Approval stage and unpublished in August 2026. Extinguishers marketed for lithium-ion are commonly tested to NTA 8133, a Dutch technical agreement limited to batteries up to 600 Wh. That can be real evidence about a specific product, and it is not a Class L rating.

Does UK law require a lithium-ion fire extinguisher?

No. Article 13 of the Fire Safety Order requires appropriate firefighting equipment for the premises and names no product. Article 9 requires the risk assessment. Whether specialist provision is justified is a conclusion your assessment reaches, not a rule you can look up.

How do you know a battery is about to fail?

Often it tells you first, though government-commissioned research is clear that a cell can also fail with no outward sign. The signs to know are swelling or a change of shape, lumps, leaks, damage to the casing, becoming extremely hot to touch, hissing or cracking, an unusual smell, smoke, or taking longer to charge than it used to. Stop using it and stop charging it. Do not move or touch a battery that is smoking, swollen, hot or damaged; keep people away from it and arrange proper disposal.

What to do on Monday

Find where batteries charge in your building and look at what is above, below and beside them, and whether anyone would walk past a fire there to get out. Write that into the fire risk assessment, because article 9(3) already requires the review and nobody is coming to tell you to do it. Then tell your staff the instruction the fire services all give, which is that this is the one fire they do not fight.

The training that supports it is not lithium-specific. It is knowing the classes well enough not to reach for the blue powder, knowing the evacuation plan, and having someone nominated who sweeps and counts. Our Fire Safety and Fire Warden Training courses cover both, and the wider picture on classes and colours is in our guide to fire extinguisher types and colours. For what the Fire Safety Order asks of you more generally, see fire safety training requirements in the UK and fire warden duties.