The spontaneous combustion of people (i.e. death from a fire originating within the victim's body without a direct external cause) is a theorised explanation for a number of unexplained cases, some of which are well-documented and many of which are not. The more convincing cases share the following characteristics:

*The body is completely or almost completely incinerated, while nearby furniture that should normally have been damaged under such temperatures remains intact.

*Damage is limited to the victim's clothing, to the area of the floor or furniture on which he or she died, and to the ceiling above the corpse.

*The torso is the focus of the fire, and if remains are found these are of the extremities, such as the feet.

*There are no traces of fire accelerant, and the fire does not have an evident external cause.

*The victim is typically alone at the time of death, and is thought to have been alive when the fire started, despite showing little sign of having struggled

Other theories speculate that the fire begins as a result of a buildup of static electricity inside the body or from an external geomagnetic force exerted on the body

A self-proclaimed expert on spontaneous human combustion, Larry Arnold, has suggested that the phenomenon is the work of a new subatomic particle called a pyroton, which he says interacts with cells to create a mini-explosion.

A possible explanation is the wick effect, which proposes that the body, when lit by a cigarette, smoldering ember or other heat source, acts much like an inside-out candle. A candle is composed of a wick on the inside surrounded by a wax made of flammable fatty acids. The wax ignites the wick and keeps it burning. In the human body, the body fat acts as the flammable substance, and the victim's clothing or hair acts as the wick. As the fat melts from the heat, it soaks into the clothing and acts as a wax-like substance to keep the wick burning slowly. Scientists say this is why victims' bodies are destroyed yet their surroundings are barely burned.