Rags or cloths soaked with linseed oil must be handled carefully. Linseed oil releases heat as it dries. Soaked rags in confined areas could combust spontaneously. Wash rags after using linseed oil.
I darn near burned down my barn by leaving a couple of linseed rags on the bench by mistake which I was using to color some black hot iron. Caught fire about 3 hours later, by chance just happened to take a look at the barn before going to bed, smoke was pouring out of the door. Got it out but just in time.. Still creeps me out, just thinking about it. Now I now you are saying "this guy must be dumb as a post, everyone knows contanimated rags can catch fire". true enough, I knew that also, but I did it anyway. Now I wash them out and then put in the burn barrel EVERYTIME.