Kay King, of Dunedin, asks :-

I heard that a fire was caused by tea towels spontaneously combusting which seems odd. Is it possible?

Colin Clemens, of the Fire Research and Investigation Unit of the New Zealand Fire Service, responded.

The "spontaneous combustion" of tea towels in restaurants is an ongoing issue that has been occurring for at least 20 years that I am aware of.

Whilst it could be argued that the use of the term 'spontaneous combustion' is incorrect in the strictest interpretation due to the influence of certain external factors, for simplicity we consider it appropriate in this area.

Essentially what happens is that tea towels are contaminated with various oils whilst in use in restaurant kitchens. Oils that provide the highest risk are those known as 'drying oils' which are most commonly of vegetable or animal origin. Fortunately however, conditions for this type of ignition do not usually occur with the cooking oils commonly found in household kitchens.

Washing the tea towels, possibly with the exception of commercial laundry facilities, fail to remove the oils, then with the addition of the heating from a dryer, often with insufficient cool down time, leaves the fabric at an elevated temperature. A simple example that illustrates this is taking bath towels out of the dyer at home and leaving them in a pile. The temperature towards the centre of the pile remains elevated for some time.

What happens with the tea towels is that the elevated temperature and the oil contamination can result in further self-heating leading to ignition if the conditions are suitable, ie lack of dissipation of heat through the material. Dont forget that in the days of sailing ships carrying wool to England, some were known to catch fire due to the "composting" heating of damp wool. There are other scenarios where contamination of fabric results in fires. Our web site www.fire.org.nz > Home Fire Safety > Investigation Unit > Heads Up Learning Documents has a "Heads Up" document on Spontaneous Combustion with Organic Oils.

Additional information is available from Kirks Fire Investigation, 7th Edition, DeHaan J.D., Pearson, 2012, pp209-213, 595.