Been to a job this morning to clean carpets with soot / carbon deposits from firemen's boots following a bedroom fire. Clients had been using linseed oil and left the oil soaked cotton rags on a plastic bag while they went to have lunch. According to the fire brigade, linseed oil, when left to it's own devices and on cotton rags, can be subject to exothermic chemical reaction within the rags. No doubt other's have heard of this, but it's a new one on me.