Spontaneous human combustion (SHC) refers to the proposed ability of the human body to burst into flames without an external source of ignition. It is a controversial idea that has no known scientific foundation, yet it appears to occur on rare occasions.
Death by alleged spontaneous human combustion has three main characteristics that differentiate it from other types of death by fire:
- Victims of proposed spontaneous human combustion incinerate so completely, even the skeleton is reduced to ashes. This does not even occur in a crematorium, where sustained temperatures of 1,300-1,800° Fahrenheit (700-1000° Celsius) leave bones that must be pulverized in a separate process, then remixed with soft-body ashes. House fires also do not consume bones.
- Damage from fire in cases of spontaneous human combustion is extremely localized. Delicate items close by the victim can remain unaffected. In one case a body was found incinerated in bed. Though the bed was destroyed, a box of tissues on the nightstand at arm's reach was untouched, along with the nightstand itself. In some cases plastic items nearby will melt, but the fire does not spread to envelop the room.
- Burns to the body are deeply inconsistent. While the body and skeleton are reduced to ashes, the lower legs often remain, appearing as the victim might have casually placed them last, clothed and shod. In other cases a torso might be left, and in many cases the skull remains along with the lower legs.
Some believe spontaneous human combustion is a natural occurrence that is not yet understood. The scientific community rejects this notion out of hand, pointing to the body's water content and no known physical trigger for combustion. Many theories have been put forth in an effort to explain alleged spontaneous human combustion in other terms. The theory that has gained the most favor to date is the wick theory.
The wick theory charges that if clothing were to begin a slow burn, noxious fumes could render a person unconscious. From here, the low-flaming fire could spread over the body, melting body fat, which would soak the clothes, turning them into a virtual wick. While the "wick" slowly burned, the body fat would keep the fire alive. Eventually, when the entire body was consumed, the fire would go out. Proponents of this theory point out that this could account for the fire's containment. They also claim it explains why the lower legs are often left, as they have little fat content.
In an attempted trial to prove the hypotheses, wick theorists used a pig carcass to simulate the theory, but were forced to call in the Fire Department when the fire rapidly spread throughout the model. In another more successful trial where the bones finally became consumed, wick theorists claimed success. However, the pig carcass was soaked in petrol before setting it alight. There is no reported evidence of petrol or other accelerants in cases of alleged spontaneous human combustion.
Critics of the wick theory find many faults with it, arguing that it does not account for a source of ignition. Neither does it explain, in all cases, the deep inconsistencies in how the bodies burn. And in some cases empirical evidence appears to rule out a wick-type event.
There are people that claim to have survived spontaneous human combustion, and many have documented their experiences. It is unclear as to whether these incidences of partial burning represent spontaneous human combustion or another theoretical event called static fire. Static fire is believed to be generated by high levels of static electricity in the body. Under certain conditions it may be possible for static charge to create a spark that might ignite flammable clothing. There are several documented cases of witnesses to spontaneous fire which might be explained by static fire. Some wick theorists claim that static fire could be the source of ignition for a wick fire.
To date there is no unopposed theory for the phenomenon known as spontaneous human combustion. Less popular explanations range from paranormal causations to alleged nuclear fusion triggered by a hypothetical subatomic particle.