LCNi reports in 2014:
Fire
Essential oils such as cloves, eucalyptus and similar products are a main feature of spa treatments.
In their pure form many of these essential oils would be classed as flammable liquids with flash points in the range 50 - 60C. The product formula usually dilutes them in a carrier oil at a concentration of 0.5 to 3%, so the final flammability depends to a large extent on the carrier being used. However, the essential oils do not dissolve in or mix with water, so the carrier oils are likely to be well able to support combustion once ignited. Essential oils are exceptionally difficult to wash out of towels, either partially or completely, so the residues remains on the wet towels when they go from washer to dryer.
Once the water has evaporated, the towel warms up and many oils will start to react with the oxygen in the drying airstream and give off heat. This (exothermic) reaction continues when the towels are unloaded into a barrow, although at this point any heat generated usually (but not always) dissipates naturally. The towels then pass to the towel folder where they are folded and stacked.
If the reaction continues, heat builds up in the centre of one or more of the stacks and the surrounding towels insulate it and prevent it dissipating. As the temperature of the centre rises the reaction develops faster and faster until eventually the whole stack ignites, exploding and hurling flaming textiles all over the laundry.
This has been advanced as one of the main reasons for the unexplained laundry fires that break out in the middle of the night.
In most laundries there are no staff on site overnight to deal with the problem so the whole laundry can burn down leading to a typical insurance bill of £5million - £10million each time.
Currently the UK laundry and rental sector loses one or two laundries a year through fire. The most likely common factor in this scenario is un-removed oil on the textiles at the seat of the blaze.