A high-risk portable appliance is any mains-powered item with a plug whose fault can let it overheat and ignite the class of equipment that Portable Appliance Testing (PAT) exists to check. Faulty electrical appliances are a leading cause of UK domestic and workplace fires, and a small set of them accounts for a disproportionate share of ignitions.
The 9 appliances below are the ones that recur in fire-service data. The people who own, manage, or test this equipment are also the people who must stay qualified and compliant, and the sections that follow explain what makes an appliance dangerous, which appliances fail most often, how a fault becomes a fire, and how testing prevents it. What actually makes an appliance dangerous in the first place is the place to start.
What Makes an Electrical Appliance a Fire Risk?
An electrical appliance becomes a fire risk when a fault lets it overheat, arc, or ignite nearby material. A portable appliance any equipment fed by mains electricity through a plug and flexible lead carries current every time it runs, and current meeting a defect produces heat where heat is not designed to go. Most ignitions trace to a short list of failure points:
- Damaged or frayed flex and cables
- Overheating from blocked ventilation or restricted airflow
- Faulty internal wiring or degraded insulation
- Overloaded plugs and extension leads
- General wear, and misuse against the maker’s instruction
The common thread is a fault or overheating condition that develops gradually. That is also why so many appliance fires are, in principle, foreseeable.
Which Electrical Appliances Cause the Most House Fires?
The following appliances, ranked by their prominence in incident data, account for most UK appliance fires a pattern documented across the Home Office Appliance Fire Dataset and London Fire Brigade’s cause-of-ignition records.
Tumble dryers
Tumble dryers fire when lint accumulates around the heating element and drum airflow is restricted, and a high-power motor adds heat; the Whirlpool-brand defect behind the 2019 recall was linked to more than 750 fires.
(By raw incident count they usually sit just behind washing machines, but they lead on claim severity and recall history.)
Washing machines
Washing machines catch fire when printed circuit boards fail, drive belts wear and overheat, or door-seal wiring degrades; London Fire Brigade recorded 92 washing-machine fires in 2025, the single largest white-goods cause that year.
Dishwashers
Dishwashers start fires when a heating-element or wiring fault arcs inside a sealed, humid cabinet, typically while the machine runs unattended overnight.
Cookers and ovens
Cookers and ovens account for the largest share of dwelling-fire ignitions cooking appliances were behind 44% of England’s accidental dwelling fires in 2024/25 (MHCLG) though most of those trace to misuse rather than appliance fault.
Microwaves
Microwaves fire when food overheats, or when a failed door interlock or magnetron allows continued operation, although the recorded fire count is generally lower than for white goods.
Electric heaters
Electric heaters cause fires largely by igniting materials placed too close to the element, rather than through an internal fault.
Chargers and phones
Chargers and phones fail through counterfeit adaptors and degrading lithium-ion cells, particularly when left charging unattended; LFB attends around 24 fires a week linked to chargers, batteries and cables.
Toasters
Toasters fire when crumb debris builds beneath the elements, or a thermostat sticks and the element stays energised after the cycle ends.
Faulty extension leads
Faulty extension leads overheat when total load exceeds the lead’s rating, or when a cable-drum lead is run without being fully unwound.
Knowing which appliances fail is one thing; how a fault turns into a fire is another.
How Do Faulty Appliances Actually Start a Fire?
A fault causes heat to build until it ignites nearby material. The chain is consistent: a faulty appliance (the agent) overheats or arcs (the mechanism), and that energy transfers to surrounding materials dust, lint, plastic housing, or the flex itself (the patient) which reach ignition temperature. Loose connections and degraded insulation raise resistance at a single point, concentrating heat in a spot the design never intended to run hot.
Because these conditions develop over weeks rather than seconds, most appliance fires are preceded by warning signs scorch marks, hot plugs, a burning smell, or breakers that trip without obvious cause (London Fire Brigade). If faults are this predictable, the question is whether they can be caught before ignition.
Can PAT Testing Prevent Electrical Appliance Fires?
Yes. PAT testing identifies the faults listed above damaged flex, insulation failure, and poor earthing before they cause a fire. A portable appliance test combines visual inspection with instrument checks of earth continuity, insulation resistance, and lead condition, which is precisely the set of defects that turns a working appliance into an ignition source. Interpreting those readings correctly is a learned skill rather than an inspection anyone can improvise.
Who Is Responsible for Keeping Workplace Appliances Safe?
Employers, landlords, and duty-holders under UK electrical safety duties are responsible for keeping workplace and rented appliances safe. A duty-holder is the party with control over the premises or equipment the employer at work, the landlord in a let property and the obligation is to keep electrical equipment maintained in a safe condition, which separates compliant appliances from dangerous, unmaintained ones.
Tenants and employees generally hold no equivalent duty for the fixed provision, though they remain responsible for their own portable items. Where an appliance is left unmaintained, the consequences are defined rather than discretionary, as set out under What Are the Penalties for Failing to Maintain Electrical Equipment at Work. General testing competence can be obtained through a PAT testing course.
Frequently Asked Questions
What is the number-one cause of house fires in the UK?
Cooking is the largest single cause. Cooking appliances were behind 44% of England’s accidental dwelling fires in 2024/25 (MHCLG), though most of those fires stem from how the appliance is used pans left unattended, heat set too high rather than an electrical fault in the appliance itself.
Which household appliance is most likely to catch fire?
Tumble dryers are commonly named the highest-risk appliance because of lint ignition and a long recall history, including the Whirlpool defect linked to more than 750 fires (2019 recall). By raw incident count, however, washing machines often edge ahead London Fire Brigade recorded them as its single largest white-goods cause in 2025.
Should appliances be left plugged in and running overnight?
Running white goods unattended is generally discouraged. Tumble dryers, washing machines, and dishwashers cause a disproportionate share of appliance fires partly because they often operate overnight, when a developing fault can escalate before anyone notices (London Fire Brigade guidance).
Are extension leads a fire risk?
They can be, when overloaded. An extension lead overheats once the combined load of the connected appliances exceeds its rated capacity, and a cable-drum lead run without being fully unwound can overheat even under a lower load.
Can a PAT test detect every electrical fault
No. A portable appliance test checks earthing, insulation, and lead condition at a point in time, but it cannot predict intermittent faults that appear only under load, or damage occurring after the test date. The limits of what an inspection covers are set out in Can a PAT Test Detect Every Electrical Fault?.
