Since the 1600s, there have been strange stories about fires in which a person burned but the room did not. Some people called this "spontaneous human combustion" and said the body started burning by itself.

Scientists do not agree with this idea. In these cases, there was always a small fire nearby, like a cigarette or a heater. Clothes can work like a candle wick, so the fire burns slowly.

For centuries, there have been reports of fires in which part of a person's body was destroyed while the furniture around it was barely damaged. This was called "spontaneous human combustion," meaning a body catching fire by itself. Forensic scientists, however, have found a simpler explanation.

In 1999, DeHaan and his colleagues burned pig fat and skin in experiments. They found that the tissue needed outside heat to start burning and a piece of cloth to act like a candle wick. Melted fat then fed a small, slow flame for a long time. Because the flame stayed small, nearby objects often did not catch fire. In real cases, a source of fire, such as a cigarette, was usually found nearby.

Since the seventeenth century, investigators have occasionally described fires in which much of a person's body was consumed while nearby furniture survived almost intact. Such cases gave rise to the idea of "spontaneous human combustion", in which a body supposedly ignites from within. Forensic research points to a more ordinary explanation.

Reviewing their own cases and earlier reports in 2011, the French forensic doctors Levi-Faict and Quatrehomme noted recurring features: the surroundings were largely undamaged, the burning usually occurred after death from natural causes, and an external source of fire was present. Experiments explain how this can happen. In 1999, DeHaan and colleagues showed that animal fat and skin would burn only after being heated by an outside flame and only with a porous wick, such as charred cloth.

Under those conditions, tissue burned at roughly one to three grams per second, producing a relatively small fire that seldom spread to nearby objects. This "wick effect" resembles a candle, in which melted wax rises through the wick. The forensic pathologist Byard has described spontaneous combustion as a myth. Even so, the exact pattern of damage depends on clothing, flooring and airflow, so individual cases can be difficult to reconstruct.