Are you safe from spontaneous combustion if you dry oily rags by laying them out flat or hanging one at time on the edge of a garbage can?
Andy Rae: As long as you don’t bundle or otherwise enclose the rag —where heat generated by the drying finish can accumulate to ignition levels — you, your rags and your shop should be fine.
Michael Dresdner: I lay mine out on the edges of tables or on a clothesline. As long as they are flat and the heat dissipates, you are in no danger. Once the rags are dry and crusty, they are no longer reacting and can then be safely put in the trash. Incidentally, this ONLY applies to drying oils. Rags with non-drying oils, such as motor oil, will never dry and get crusty, and are generally not permitted in household trash. Of course, they are also not candidates for spontaneous combustion, though they are quite flammable.