Spontaneous Ignition

The classic example of spontaneous ignition is linseed oil on rags. Linseed oil is used with paints or as a wood treatment all by itself. During the painting process one cleans up their messes with rags. The linseed oil on these rags then reacts with oxygen in the air. This chemical reaction gives off heat. If the rags are laid out on the floor or not put in a pile, the heat given off is released harmlessly into the air. But, if the rags are cleaned up and thrown into a garbage can or a box, that heat is not so easily released. When that energy is stored in the rags they become warmer, the chemical reaction speeds up, and then before we know it this simple pile of rags has ignited – potentially causing a fire.

The key concepts to spontaneous ignition have already been alluded to in the linseed oil and rag scenario above. Those concepts are:

• The need for a chemical reaction that gives off energy
• A storage scenario that leads to heat being stored in the material that could potentially ignite
• A source of oxygen

So, if all three of these factors exist, what determines if the material will ignite? From a scientific standpoint, it has to do with the rate at which energy is generated versus how quickly the energy can be lost. If it is lost as quickly or more quickly then the material most likely won’t ignite. If the energy generation is greater than what can be lost from the system, then the material heats up and may ignite and burn.