Why is tumble dryer lint a fire risk, and what must I do about it?

It is easy to treat lint as a housekeeping matter — a bit of fluff in a tray. Physically it is something else: an extremely fine, extremely dry cellulose and polyester fibre with an enormous surface area relative to its mass, which is what makes it ignite readily. It collects inside a machine whose job is to blow hot air, and the accumulation and the heat reinforce one another. That loop is why this is a safety topic rather than a cleaning one.

Safety

What you'll need

• Vacuum with a crevice tool
• A soft brush
• Warm soapy water for the filter
• A torch (optional)

Step by step

1. Understand the loop before the checklist.Lint restricts airflow. Restricted airflow means the heater cannot shed its heat into moving air, so the machine runs hotter and for longer. Longer, hotter running produces and traps more lint, closer to the hot parts. Each cycle makes the next one worse.
2. Clean the filter after every single load.Not most loads. Every one. It takes five seconds and it is the single most effective thing anyone does about this risk.
3. Wash the filter in warm soapy water monthly.Fabric conditioner and dryer sheets leave an invisible film across the mesh that restricts airflow while the filter looks perfectly clean. Wash it, rinse it and dry it fully before refitting.
4. Vacuum the housing beneath and behind the filter.Unplug the machine first. Lint mats into the recess below the filter where it cannot be pulled out by hand, and it is one of the closest accumulations to the airflow path. A crevice tool clears it in a minute.
5. Keep the condenser or secondary filter clear.Condenser units rinse out under a tap monthly. Heat pump machines have a second filter and a set of evaporator fins behind the plinth panel that clog with a fine grey mat; the manual explains the method for your model.
6. On a vented machine, keep the hose and grille clear.Lint settles along the length of a vent hose, and a crushed or over-long hose traps far more of it. Outside, check the flap opens freely and is not blocked by debris, cobwebs or nesting.
7. Never run a dryer unattended.Not overnight, not while out, not while everyone is asleep. This is the rule fire services repeat, and it is the difference between a fault that is noticed and one that is not.
8. Never tumble anything contaminated with oil or solvent.Cooking oil on tea towels, engine oil on overalls, petrol, white spirit, wood stain, massage oil on towels. Washing reduces but does not remove enough oil. Residual oil in warm fabric oxidises, generates its own heat, and can ignite in a pile after the machine has finished. Line dry these items instead, always.
9. Take rising drying times as a warning.A machine that used to take ninety minutes and now takes three hours is telling you its airflow is restricted, which is the same condition that makes it run hot. Do not simply set a longer timer.
10. Give the machine room to breathe.Air intakes and outlets clear, a gap around the machine, and never shut inside a cupboard without ventilation. A dryer that cannot draw cool air runs hotter for the same work.
11. Unload promptly and let the load cool.A hot load left compressed in a closed drum or dumped straight into a basket holds its heat. The cool-down phase at the end of a cycle exists for a reason; do not skip it by opening the door early and leaving the load in.
12. Check whether your model has ever been subject to a recall.Search the manufacturer's site with the model and serial number from the rating plate, and register the appliance so you are contacted directly if a safety notice is ever issued. This takes five minutes once.

Tips

• If you cannot remember to clean the filter, keep the machine's door area clear and make emptying the filter part of unloading, in the same motion. Habits attached to an existing action survive; standalone ones do not.
• Reducing or stopping fabric conditioner cuts the filter film substantially, which keeps airflow up and drying times down as well as reducing the risk.
• A smoke alarm in or adjacent to a utility room or kitchen containing a dryer is a sensible thing to have and to test. Heat alarms are the appropriate type for a kitchen.
• Lint is genuinely useful as a firelighter for a wood stove, which is a good demonstration of the point being made here.

Common mistakes

• Running the dryer overnight or while out — It is the single behaviour that turns a fault into a fire nobody is there to notice. Convenience is not worth it, and timers can be set to finish while you are at home instead.
• Tumble drying oily cloths after washing them — Washing removes the visible oil and leaves enough behind to matter. Oil-contaminated fabric self-heats as it oxidises, and a warm pile of it after the cycle ends is where ignition happens.
• Assuming a clean-looking filter is clean — Fabric conditioner leaves a transparent film across the mesh. Hold it up to the light — if it looks hazy rather than open, it is restricting airflow.
• Treating longer cycles as the machine getting old — It is the machine telling you its airflow is restricted, which is the exact precondition for overheating. It is a symptom to act on, not to adapt to.

Questions people ask