We have had a spate of spontaneous combustion ignited fires in our small community lately. One local town has had at least four confirmed spontaneous combustion fires in the last 6 months. One of the recent fires destroyed an apartment building “when rags containing an organic or vegetable-based oil were placed wadded up in a carboard box after they were used to refinish a floor.”
See the local story here.
There was also a fire at a local carpet store a few years ago, which I know was also started due to spontaneous combution of oil soaked rags.
Lindseed oil is one of the worst offenders. The oil soaked rags can ignite with no external heat source within 5 – 10 hours after use. These oils are typcially associated with wood finishing.
The safest way to deal with oil soaked rags is to put them in an airtight metal container filled with water. Another method is to lay them flat on a concrete surface and allow them to dry for a few hours after which they can be disposed of. If they are left to dry, you must be careful to not let them be blown into a pile, where they could ignite.