Some hypotheses attempt to explain how SHC might occur without an external flame source, while other hypotheses suggest incidents that might appear as spontaneous combustion actually had an external source of ignition – and that the likelihood of spontaneous human combustion without an external ignition source is quite low.[8] Benjamin Radford, science writer and deputy editor of the science magazine Skeptical Inquirer, casts doubt on the plausibility of spontaneous human combustion, "If SHC is a real phenomenon (and not the result of an elderly or infirm person being too close to a flame source), why doesn’t it happen more often? There are 5 billion (editor's note: as of 2011) people in the world, and yet we don’t see reports of people bursting into flame while walking down the street, attending football games, or sipping a coffee at a local Starbucks."[9] Paranormal researcher Brian Dunning states that SHC stories "are simply the rare cases where a natural death in isolation has been followed by a slow combustion from some nearby source of ignition." He further suggested that reports of people suddenly aflame should be called "Unsolved deaths by fire," stating that the cause being unknown did not necessarily imply that it had not resulted from an external ignition source.[10]
Natural explanations[edit]
Almost all cases of SHC involve persons with low mobility, due to advanced age or obesity, along with poor health.[11] Victims show a high likelihood of having died in their sleep, or of being unable to move once they had caught fire.
Cigarettes are often seen as the source of fire, as the improper disposal of smoking materials causes one of every four fire deaths in the USA.[12] Natural causes such as heart attacks may lead to the victim dying, subsequently dropping the cigarette, which after a period of smouldering can ignite the victim’s clothes.[13]
The "wick effect" hypothesis suggests that a small external flame source, such as a burning cigarette, chars the clothing of the victim at a location, splitting the skin and releasing subcutaneous fat, which is in turn absorbed into the burned clothing, acting as a wick. This combustion can continue for as long as the fuel is available. This hypothesis has been successfully tested with animal tissue (pig) and is consistent with evidence recovered from cases of human combustion.[14][15] The human body typically has enough stored energy in fat and other chemical stores to fully combust the body; even lean people have several pounds of fat in their tissues. This fat, once heated by the burning clothing, wicks into the clothing much as candle wax (which typically was originally made of animal fat) wicks into a lit candle wick to provide the fuel needed to keep the wick burning.[16] The protein in the body also burns, but provides less energy than fat, with the water in the body being the main impediment to combustion. However, slow combustion, lasting hours, gives the water time to evaporate slowly, which require less energy than boiling the water off quickly would. In an enclosed area, such as a house, this moisture will recondense nearby, such as on windows.[citation needed] Note that feet often have the least fat, so don't typically burn. (Hands also have little fat, but may burn if on the abdomen, which provides all the needed fat.)
Scalding can cause burn-like injuries, including death, without setting fire to clothing. Although not applicable in cases where the body is charred and burnt, this has been suggested as a cause in at least one claimed SHC-like event.[17]
Brian J. Ford has suggested that ketosis, possibly caused by alcoholism or low-carb dieting, produces acetone, which is highly flammable and could therefore lead to apparently spontaneous combustion.[18][19]
Sometimes there are reasonable explanations for the deaths, but proponents ignore official autopsies and contradictory evidence, in favor of anecdotal accounts and personal testimonies.[13][20][21]
Unverified natural phenomena[edit]
Larry E. Arnold in his 1995 book Ablaze! proposed a pseudoscientific new subatomic particle, which he called "pyrotron".[3]:99–106[21] Arnold also wrote that the flammability of a human body could be increased by certain circumstances, like increased alcohol in the blood.[3]:84[21] He also wrote that extreme stress could be the trigger that starts many combustions.[3]:163[21] This process may use no external oxygen to spread throughout the body, since it may not be an "oxidation-reduction" reaction,[citation needed] however, no reaction mechanism has been proposed. Researcher Joe Nickell has criticized Arnold's hypotheses as based on selective evidence and argument from ignorance.[21] |
