Feb 132015
 

Everyone knows, or should know, that rags contaminated with certain types of oil can self-ignite,or spontaneously combust, in places like waste bins but freshly-laundered tea-towels can also do so and lead to a galley fire warns a safety alert from Marine Safety Forum.

A night watchman on a vessel was carrying out his usual tasks and after washing the galley tea towels, they went into the tumble dryer. Once finished approximately 20 tea towels were stacked in a pile and placed on top of the galley freezer.

Between three and four hours later, the night watchman discovered smoke coming from the pile of tea towels. This was quickly dealt with and four to five tea towels in the very centre of the pile were found to be scorched and smouldering. The crew member also stated that the top of the actual freezer was not hot in any way.

We know oil contaminated cotton cloth or overalls can spontaneously combust in certain circumstances. Not all oil types cause this effect, the main ones that do are; Linseed oil, rapeseed oil, safflower oil – a vegetable oil ingredient and peanut oil.

Fish oils are also notorious for self-heating. However mineral oils used for lubrication are not prone will not cause spontaneous combustion.
Generally, the build-up of heat to ignition point occurs when the material is in a pile so that the heat being generated cannot adequately escape. In fact, fires in commercial laundries, and sometimes in hospitals and laundromats have been attributed to the spontaneous ignition of cotton or linen that has been dried and then either stacked while still hot or dumped into bins without cooling.
The oxidation of cotton and linen can be initiated by the laundry process. If the materials are stacked or binned at high enough temperatures, typically 90 Celsius, the heat accumulated in the centre of the pile may be enough to trigger spontaneous ignition of the cotton materials.
If towels and linen that contain oil such as cooking oils or the oils from physiotherapy or massage clinics are sent for laundering, a residue of oil may remain after the laundering process. The heating and drying after laundering may cause this residue to self-heat and spontaneously ignite.”
Uncontaminated cotton or linen can spontaneously combust if piled up when still hot straight from a tumble drier. It is likely in this case that there was some contamination from cooking oil still on the tea towels in the centre of the pile and enough residual heat from the tumble drying process remained to start the exothermic reaction that resulted in the scorching.
This is initially a slow process hence the three to four hour delay before smoke was seen.
In laundries, the washing should be spread to cool after it has been dried, not placed in bins or piles while still hot.

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See also:

Safety Alert – Watch Those Oily Rags

 

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