Commercial laundry fires have an unusual signature: a large proportion of them start in clean linen, after processing, with no external ignition source involved at all. The mechanism is spontaneous combustion, and it depends on a specific and very common combination of conditions that laundry operations produce routinely without recognizing what they are creating.
Fabric that carries residual oil, and this includes massage and spa linens, restaurant aprons and towels, salon capes, and anything from a kitchen or maintenance context, undergoes slow exothermic oxidation. Under normal circumstances the heat dissipates and nothing happens. Tumble the fabric hot, then fold and stack it while it is still warm, and the stack becomes an insulated mass with a heat-generating reaction inside it and no path for the heat to escape. Temperature climbs until the fabric reaches its ignition point, typically hours after the shift ended and the building emptied.
The second hazard is lint, which is a fine, dry, well-aerated Class A fuel that the process generates continuously and deposits inside the exhaust duct system. Lint accumulation restricts airflow, which raises dryer temperature, which increases both the self-heating risk and the chance of ignition inside the dryer itself. A dryer fire then has a duct full of lint running into the building structure as a ready-made propagation path. In South Florida’s hotel, resort, and cruise provisioning market these are very high-volume operations, which means both hazards run continuously.