At the end of a long day we all look forward to grabbing our coats and heading home for the evening to relax. Unfortunately, there can be hidden dangers left behind if we are in too much of a hurry.
Imagine the scenario of painting the trim and doors of a suite of offices with an oil based varnish over several days. Each evening you grab the oily papers and rags used to protect the floors and clean the brushes and stuff them in a plastic bag and dump it in the bin.
Those papers and rags may contain drying oils which oxidize and in doing so generate heat.
That in itself is not that bad on a smooth surface where the heat can dissipate. Oxidation is a common process and in the majority of cases the heat formed is quickly and easily dissipated. Take the case of rust forming on steel - the oxidation process is slow and any heat produced is so small that normally spontaneous combustion would not be an issue.
If, however, oxidation takes place in a confined space, where thin layers of oil are exposed to air providing maximum oxidation, the heat begins to build and will continue to do so until it reaches the spontaneous combustion temperature. A bundle of paper and rags can ignite and may result in major damage and possible threat to life.
Similar problems are known to occur in other combustible materials such as haystacks and heaps of straw and saw dust. Here oxidation can be induced by bacteriological attack through fermentation creating ignition heat which may destroy most of the bacteria but can still result in fire.
Paints based on oils and alkyds produced from Tung oil, Linseed and Soya bean are particularly susceptible to this problem which can have devastating consequences.
Spontaneous combustion is caused by a combination of:
It is good practice to assume that all solvent based, oil based or flammable products are possible sources of spontaneous combustion. The care and disposal of soiled materials from these jobs is critical to the welfare of the site and the people working on it.
Spontaneous combustion can be avoided by:
Not all products are prone to spontaneous combustion but it pays to be cautious. Examine the labels on cans carefully to look for warnings and if in doubt follow the guidance above. It may take an extra couple of minutes but is well worth the time to avoid a major accident.
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