As this is published, the Met Office has an amber extreme heat warning in force across southern and eastern England, including London and the East, for Monday 22 and Tuesday 23 June, with temperatures forecast into the mid 30s and a real chance of the June record being broken. Most heatwave guidance, rightly, concentrates on protecting people from the heat itself. There is a second risk that attracts far less attention and sits squarely with the person responsible for your premises: hot, dry conditions make fire both more likely to start and faster to spread.
Why extreme heat changes the fire picture
Fire needs fuel, oxygen and a source of ignition. A prolonged spell of hot, dry weather quietly tips all three in the wrong direction. Materials that are usually too damp to catch will dry out and ignite more easily. Equipment runs hotter and works harder. People change how they use a building, propping doors and windows open for air, and some of those habits undo fire protection that was carefully designed in. None of this is dramatic on its own. Across a few very hot days, though, it adds up to a higher chance of a fire starting and a quicker spread once it does.
Combustible materials and outdoor ignition
Dry vegetation, accumulated waste, cardboard, packaging, sawdust and timber all become easier to ignite during a heatwave. Yards, car parks, storage compounds and the ground around buildings are common starting points, often from a discarded cigarette or a stray spark. Keep waste cleared rather than left to build up, watch dry grass and vegetation near buildings and boundaries, and confine smoking to designated areas with proper receptacles. On construction sites and in landscaping work, the combination of dry ground and hot works deserves particular care, with a permit system and a proper fire watch after work finishes.
Equipment, electrics and batteries
Electrical systems and machinery generate their own heat, and a hot environment gives that heat nowhere to go. Motors, plant and electrical installations can overheat, and the surge in portable fans and mobile cooling units adds load to circuits and sockets that may already be working hard. Avoid daisy-chained extension leads, watch for overloaded sockets, and keep ventilation clear around equipment that needs to shed heat.
Lithium-ion batteries deserve a special mention. The tools, power banks, e-bikes and electric vehicles now common on sites and in workplaces all depend on them, and high temperatures raise the risk of thermal runaway, where a battery overheats, ignites and is very difficult to extinguish. Do not charge or store batteries in direct sun or in hot, enclosed spaces, do not leave them on charge unattended overnight, and take any battery that is swollen, damaged or unusually hot out of service straight away.
Flammable and dangerous substances
Solvents, fuels, gas cylinders, aerosols and other flammable substances behave differently in the heat. Liquids give off more vapour, and pressurised containers can expand and vent. Keep flammable stock out of direct sunlight, in ventilated storage away from ignition sources, and within the quantities your assessment allows. If you store or use dangerous substances, a heatwave is a good prompt to confirm that your controls under DSEAR are being followed on the ground, not just recorded on paper.
When propping fire doors backfires
On a hot day the temptation to wedge internal doors open for a through-draught is completely understandable. It is also one of the quickest ways to undo your building’s fire protection. Fire doors are there to hold back fire and smoke and to keep escape routes usable, and they only do that job when they are closed. Propping them open removes the compartmentation that is meant to contain a fire to the area where it starts.
If airflow is the problem, solve it without defeating the doors. Fit approved hold-open devices that release automatically when the alarm sounds, rather than wedges or, as is still seen far too often, a fire extinguisher used as a door stop. A heatwave is also a sensible moment to confirm that your doors and barriers are in good order, since gaps and damage that reduce their performance are easy to overlook until they matter. Our pages on fire door inspections, compartmentation surveys and fire stopping explain what good looks like.
Keep escape routes and evacuation working
Heat changes behaviour around exits too. Final exit doors get propped for air, escape routes get used as a shortcut to a shaded break area, and fans or coolers can end up partly blocking a corridor. Walk your escape routes during the hot spell and make sure they are clear, unobstructed and unlocked from the inside, and that everyone still knows the plan if the alarm sounds.
Does your fire risk assessment account for hot weather?
Most fire risk assessments are written for normal conditions and never revisited for a heatwave. They should be. A suitable and sufficient assessment is a legal requirement for almost every workplace, and reviewing it when conditions change significantly, such as an extended period of extreme heat, is part of keeping it current. If yours does not consider seasonal factors at all, that is worth addressing now rather than after an incident.
Responsibility for this sits with the responsible person under the Regulatory Reform (Fire Safety) Order 2005, usually the employer, building owner or occupier. If you are unsure what the law expects, our guide to fire risk assessment requirements sets it out, and our fire risk assessment service can help you get it right.
A practical heatwave fire-safety checklist
- Clear waste, dry vegetation and combustible clutter from around buildings and boundaries.
- Confine smoking to designated areas, and apply strict hot-works discipline with permits and a fire watch.
- Keep ventilation clear around plant and electrical equipment, and avoid overloaded sockets and daisy-chained leads.
- Charge and store lithium-ion batteries out of direct sun, never unattended overnight, and retire any that are damaged or swollen.
- Keep flammable substances shaded, ventilated and within assessed quantities.
- Never prop fire doors with wedges or extinguishers. Use approved hold-open devices linked to the alarm.
- Walk escape routes daily during the heat and keep them clear and usable.
- Review your fire risk assessment for the conditions, and act on what it tells you.
Hot weather rarely gives much warning, and the businesses that come through it well are the ones that planned for it. A short briefing, a quick walk round and an up-to-date assessment will do far more to keep your premises safe than any amount of reacting on the day.
