Matt Partridge is head of product development at Armorgard UK
Last year, UK fire brigades attended 1,760 lithium-ion battery fires, according to data gathered by global business insurer QBE. That’s one callout roughly every five hours, leading the London Fire Brigade to name it the capital’s fastest-growing fire risk.
The National Fire Chiefs Council has been blunter: fundamentally, safety standards haven’t kept pace with the speed of battery adoption across industry.
Anyone working in construction knows how fast the shift has happened. Cordless tools now account for more than 80 per cent of professional power tool sales in the UK, up from roughly half a decade ago.
Drills, saws, access equipment and scanners – most of these now run on lithium-ion cells. The technology has transformed how sites operate, and the risk profile has changed with it. But not everyone has caught up.
Three ways batteries fail
It’s well documented that lithium-ion batteries fail for three reasons: physical damage, electrical faults and thermal failure. The first two are reasonably understood by site teams. However, thermal failure should be keeping contractors and their project managers awake through the recent spells of hot summer days and nights.
Battery overheating degrades cells slowly, without visible warning. Manufacturer manuals typically place the safe charging window at 15 to 30°C, close to the temperature band people find comfortable. Outside that range, degradation accelerates. Left unchecked, this can trigger thermal runaway: a chain reaction in which the battery generates heat faster than it can release it. Once it starts, it’s extremely difficult to stop.
Cool it
Ventilation performs two separate, vital functions. First and foremost, it prevents heat building up during charging. Chargers and batteries produce heat as a by-product of the charging process and, in poorly ventilated spaces, that heat accumulates. Add ambient summer temperatures to this and you can push batteries past their safe operating range without anyone realising.
Second, if a cell starts to fail, it releases gases. In a sealed or poorly ventilated enclosure, those gases pressurise, meaning the risk of explosion exists before a visible fire has started.
So, it stands to reason that having good ventilation allows those gases to escape, and should be seen as a fundamental safety requirement whatever the site or situation.
The site amplifier
A battery fire on its own is serious, but it’s something else entirely on a construction site.
Just to highlight the acute risk, lithium-ion fires can burn at over 1,000°C. As you can imagine, at that temperature, dry timber framing, combustible dust and insulation materials need very little prompting to ignite.
There has been some work to try and mitigate the risk. ISO 3941:2026, adopted by BSI earlier this year as the updated international fire classification standard, introduced a new Class L category for lithium-ion battery incidents, which applies because these fires behave differently from Class A, B or C events. They resist extinguishing, can re-ignite readily and produce toxic gases.
As such, segregation should be the immediate standard response, and something that should be simple to achieve whatever site you’re working on. The same logic that keeps gas bottles and fuel bowsers away from adjacent structures applies to battery charging areas. In most other hazard categories this is accepted practice. However, it’s not the case when it comes to lithium-ion batteries, and that needs to change, fast.
Changing summer weather
Heat is the main risk, but the same climate patterns producing record heat are also delivering heavy downpours, rapid heat-dry cycles and localised storms. Water ingress into charging equipment or a damaged battery casing is a real failure pathway, one that is easy to overlook when the sun comes back out.
The standards have moved. Class L is now the benchmark for lithium-ion fire events in the UK. The question every site manager should be asking as summer continues is simple: have your storage practices moved with the standards?
