Cold Water on a Hot Topic

the Skeptic, Vol 18 No 4

by Barry Williams

It is not often that a Skeptic can experience the sensation of fulfilment that comes with seeing one of our areas of interest finally laid to rest, but some of us must have felt it when we viewed Spontaneous Human Combustion (SHC) on ABCTV (November 11, 1998). Originally produced for the BBC, the programme went somewhat further than a similar programme of several years ago and may well have provided the final explanation for a long-term mystery.

For those unfamiliar with the concept, throughout history there have been cases of the remains of people being found, usually in closed rooms, with the majority of their bodies reduced to ash, only some outlying pieces, like the lower legs, remaining unconsumed, and with no serious damage to the other contents of the room.

This phenomenon had been quite baffling to fire investigators until recent years and, given that human beings are such curious animals, this mystery has spawned many strange explanations. They range from the moderately sublime to the patently ridiculous. On one end of this spectrum, it has been seriously suggested that a build-up of methane in the intestines could be, in rare cases, somehow ignited by enzyme activity. This suggestion was laid to rest in the earlier programme by a physiologist pointing out that such an effect would surely have shown up in a rash of cattle bursting into flames, that species being far more prolific methane generators than human beings. At the other end of the spectrum were suggestions of some sort of unknown cosmic energies (that staple of the crank pseudoscientist) being involved.

Indeed the notion that human beings spontaneously burst into flames has never had much going for it and in almost every reported case, there has been a very obvious source of ignition present. But the phenomenon retained its mystery because of the almost total reduction of a human body to ash.

Sober forensic anatomists were attracted to the idea of a purely localised fire, started by a careless cigarette or contact with an open fire, slowly consuming the body, with clothing or bedding acting as a wick, and body fat acting as fuel. This appeared to be a reasonable explanation, though there seemed to be some confounding evidence. Fire investigators pointed out that even after very fierce domestic fires, human remains were still recognisably human and, though badly charred, sufficient parts of the bodies remained to establish the cause of death. Other evidence was adduced that after cremations, in which bodies had been subjected to very high temperatures, bones still had to be reduced to granules in a ball mill, because bones tend to be quite fire-resistant.

This programme followed an experiment conducted by Dr John de Haan, of the California Criminalistics Institute, who had investigated a real murder case in which a body was found burning, unusually for ‘SHC’ cases in that it was found outdoors. In his experiment, the carcase of a fully grown pig (selected because pigs and humans have similar fat distribution) was wrapped in a blanket, deposited on a carpet, and set alight in circumstances that matched those in various ‘SHC’ cases.

And a remarkable demonstration it turned out to be. After some time, when common sense should have told us that all the blanket and carpet should have been reduced to ash, we could see pig fat bubbling from the carcase, soaking the charred material, thus acting exactly as a candle wick. It maintained a hot, though low-flame, fire and it kept doing so for hours. After around five hours the mystery of the bones began to unravel. The bone marrow (about 80% fat) was contributing to keeping the fire going, and was leading to the reduction of the bones themselves to ash. And the element that is missing in crematoria is present in these cases - time. Cremations last about 1.5 hours, but in ‘SHC’ cases the fire burns for many, many hours.

The mystery of why lower limbs so often remained after one of these fires, was explained by the low fat content of these parts and their remoteness from the seat of the fire - there is not much fat in shins and feet to sustain this sort of fire. Why rooms in which such fires occurred showed certain classical signs - nearby items not being burnt, TV sets and wall clocks showing signs of melting, but not of burning, was accounted for by the low intensity and localised nature of the fire, leading to a very hot layer of gas products in the upper part of the room. The fire is localised to the body and its immediate environment, heat builds up, but it is not enough to cause other items to ignite, only to scorch or melt.

Of course, there must be many other cases that start in similar circumstances, in which other parts of the room do catch alight and then you have a classic house fire. But no one has ever suggested that there is anything mysterious about houses catching fire and the occupants being burnt to death - careless cigarette smoking in bed, electrical faults, arson - all have plenty of substantiated cases. Only in very rare cases have physical circumstances allowed the fire to remain localised and has there been sufficient time for the body to have been reduced to ashes (in almost every case where SHC has been offered as an explanation, the victim has been alone in the house).

This was a classic example of good science; making an hypothesis and testing it. And this test showed exactly what the hypothesis had predicted, and so should set at rest at least one of the myths that has exercised the minds of some who would invest the world with unexplainable energies or other mysterious factors.

One other item of note, was that this particular belief may very well be culturally specific. We are often asked if some paranormal beliefs are peculiar to one country or another, and, outside of the obvious ones, it is difficult to determine if this is the case. However, in this case, we may have a partial answer. Dr Dominic Dehane, a forensic scientists at the Police Science Laboratory in Toulouse, when asked about SHC cases in France, said: "It is only in America and Great Britain that people believe in the myth of spontaneous human combustion. In the rest of the world we never hear about that."

As Skeptics we should be happy that there is one fewer fronts on which to carry on the struggle, but it would be an optimist indeed who believed this will be the case. No one who has invested so much of his personal belief into inventing the notion of mysterious cosmic energies is likely to be deterred by mere evidence.

See also:

The Skeptic's Dictionary - Spontaneous Human Combustion