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For decades, fans of the paranormal have debated the supposed phenomenon of "Spontaneous Human Combustion" (SHC), in which people have apparently burst into flame from the inside, and are consumed almost totally while their surroundings remain unburnt. One of the most famous of these cases is that of Mary Reeser, who lived right here in St Petersburg, Florida, just half a mile from my apartment.

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The apartment building on Cherry Street where Mary Reeser died.

On July 1, 1951, Dr Richard Reeser was visiting his mother Mary at her apartment in St Petersburg, Florida. The recently-widowed 67-year-old had just moved to Florida from Pennsylvania the year before. Dr and Mrs Reeser were joined by Mrs Pansy Carpenter, Mary Reeser's landlady who lived in the same building. When the two visitors left at 9pm, Mary had just taken two sleeping pills, and told her son she would take two more and have a cigarette before going to bed. When Richard last saw her, she had changed into her nightgown and was sitting on an easy chair, smoking a cigarette, with two electric fans pointed at her.

Later that night, at about 5am, Mrs Carpenter woke up in her apartment and thought she smelled smoke. Thinking it was coming from a water pump in her garage that had been overheating, she walked over, turned off the pump, and went back to sleep.

At 8am the next morning, Carpenter was awakened by a telegraph delivery boy who had a cable to deliver to Mary Reeser. Carpenter signed for the message, walked over to Reeser's apartment, and knocked.  There was no answer, and Carpenter noticed that the doorknob was warm to the touch. Two housepainters were working at a nearby building, and came over to help. When they forced the door open, they found a burnt-out easy chair, and a pile of ashes around it containing an intact left foot, still in its satin bedroom slipper. (Later accounts claimed that a skull had also been found in the ashes, mysteriously "shrunken" by the heat--but the presumed "skull" turned out to be just a conglomerated lump of ash.) It was the remains of Mary Reeser. A five-foot wide circle of carpet immediately under the chair had been burned away, revealing the cement floor, but the rest of the apartment showed little damage--there was soot on the walls and ceiling at a height of about four feet, a few plastic items had been softened by heat, and one of the nearby wall sockets had melted, stopping a clock that was plugged into it at 4:20am. A pile of old newspapers stacked on the floor nearby, however, were undamaged.

The St Petersburg Police were stumped. One investigator they consulted, anthropologist Wilton Krogman of the University of Pennsylvania, estimated that such a complete cremation of the body would require a temperature of at least 1,500 degrees, and had no explanation how such a fire could happen without consuming the rest of the apartment as well.

Since that day, Mary Reeser has become the iconic example of "spontaneous human combustion".  According to the SHC theory, under some unknown circumstances, the human body (with a normal body temperature of 98.6 degrees) suddenly produces a large quantity of heat from some internal source that causes its own tissues to ignite, entirely consuming the body in a short time, and then immediately extinguishes, producing no fire damage to its surroundings.  Several presumed cases of SHC can be found in "paranormal" books and websites--and Mary Reeser is usually their Case Number One.

The exotic theories introduced by paranormal fans to "explain" SHC include everything from hypothetical subatomic particles called "pyrotrons" which supposedly explode into flame when they collide with body tissues, to the ignition of methane gas inside the intestines, to some sort of nerve malfunction that produces a large electrical current and subsequent flame. None of these, alas, are plausible. "Pyrotrons" are only a fantasy--they've never been shown to even exist. The methane in human intestines has no ignition source, can't burn anyway in the absence of oxygen--and even if it did it doesn't produce a flame hot enough or long enough to ignite flesh. And the human nervous system is simply incapable of producing a voltage high enough to cause that much heat. In addition, the human body itself is remarkably resistant to burning--it is, after all, almost two-thirds water.

The very core of presumed SHC "cases" is that there is allegedly no external source of heat--the body is supposed to just burst into flame all by itself. Investigation of all the most famous cases of SHC, however, shows that there was in fact in each instance a nearby ignition source--a space heater, an electric arc, matches, or, in Mary Reeser's case, a cigarette. But the other defining characteristic of SHC is the completeness with which the body is burned, and the lack of any fire damage to the surrounding area. This, more than anything else, is what invites the paranormal claims surrounding the phenomenon.

The most likely cause of so-called "Spontaneous Human Combustion" cases was, however, already known and proposed just a few weeks after Mary Reeser's death. Unable to determine the cause of the fire, the St Pete Police had packed all the available evidence, including Mrs Reeser's ashes and remains, the burned-up chair, and samples from the carpet, and sent it to the FBI lab in Washington DC. The FBI determined that there was no gasoline or other flammable liquids on any of the debris. But they noted that Mrs Reeser, at 170 pounds, had a high amount of body fat, and that the nightgown and housecoat she had been wearing were both made of flammable acetate materials. The FBI lab concluded that she had fallen asleep, and was killed when her still-burning cigarette ignited her clothing, setting the chair on fire (the fire was probably fed extra oxygen by the fans). She likely would have died almost immediately from inhaling the flames and toxic smoke. This, by itself, would not have been hot enough to have completely incinerated the body to ashes. But then, the FBI concluded, an unusual phenomenon had happened, which would indeed have produced such temperatures.

The phenomenon is called a "wicking effect". When body fat is heated, it turns into a flammable liquid that acts in the same way that melted wax does in a candle. In effect, Mary Reeser's body had become a large candle--the melting fat soaked into the cloth remnants of her clothing, which acted as a wick. Although this would have produced only a small flame, like a candle, it would have burned at a very hot temperature, and would have continued burning as long as the supply of melted fat gave it fuel. Mrs Reeser's body, the FBI concluded, had burned like the wick in a camping stove for hours, which slowly consumed the entire body at a temperature high enough to turn even her bones into ash. The rest of the apartment had not suffered any fire damage because the actual flame was very small and localized in one spot--like a candle, the heat would not have extended more than a few inches from the flame. The hot air would have risen to the ceiling level, where it deposited soot and melted some objects that were located off the floor, but the floor level itself would have stayed cool--explaining why the nearby newspapers didn't catch fire. And the "wick effect" also explains why Mary Reeser's foot was found intact (a phenomenon found in several other cases of SHC)--the lower legs have very little fat, and would not be likely to ignite. And since Reeser was sitting up at the time of her incineration, the heat would have traveled upwards away from her feet.

At a stroke, the "wicking effect" explains all of the supposedly "mysterious" attributes of Spontaneous Human Combustion.

But the wicking effect is no mere theory--it has been experimentally demonstrated. In a study published in 2001 in the Journal of Forensic Sciences, researchers at the California Department for Forensic Services wrapped a pig carcass in clothing and set it afire. Just as the hypothesis predicted, the pig fat melted into the cloth and formed a circular wick, which burned with a slow small flame for several hours, reaching recorded temperatures of over 1,800 degrees, before being deliberately extinguished for study. The portion of the pig that had burned was completely reduced to ash--bones and all--while the remaining portions were undamaged.

But even before that experiment, the "wicking effect" had already been seen in an actual human victim--as it was happening. In 1991, a man in Oregon killed a woman out in the woods, doused her body with lighter fluid, and set her afire. Several hours later, a pair of hikers came upon the body--which was still burning. The entire center of the body, from the chest to the upper thighs, had already been reduced to ash, and small fires were still burning at the edges of the remaining sections--fueled by fat seeping into the clothing, exactly as expected from a "wicking" fire.

Stories of Spontaneous Human Combustion are entertaining and make great Halloween spooky-stories for magazines and newspapers.  But alas, as with so much of paranormal pseudoscience, actual investigations always show that there's no "there" there.

Originally posted to History for Kossacks on Wed May 07, 2014 at 01:51 PM PDT.

Also republished by SciTech.

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