Spontaneous combustion: fact or legend?

English - February 21, 2023
Image 1. Spontaneous combustion: fact or legend?

Although traditionally referred to simply as “Spontaneous Combustion”, the correct term should be “Human Spontaneous Combustion” (HSC) because spontaneous combustion in general refers to any object that can become engulfed in flames without an obvious cause or trigger. Many materials will, under the right circumstances, spontaneously combust.

People are another matter. Although the debate on spontaneous combustion has been going on for about three centuries (in which there are just over two hundred relatively well-documented cases), a priori it would be logical to deny the very possibility that a human body (composed of more than 70% water) can burn autonomously, and the fact is that many times the bodies burned in fires clearly show us that once the external source of fire was extinguished, the person’s body did not continue burning on its own.

However, a closer look seems to indicate that, although it sounds impossible, spontaneous combustion could at least be theoretically possible in some specific scenarios, thus justifying a handful of otherwise inexplicable cases (some of which were discussed in the past Spontaneous Combustion article).

In general, it should be noted that Spontaneous Combustion usually occurs in a partial manner, pulverizing to ashes one part of the body and leaving others intact. This is what has made it so difficult to explain. Let’s see:

The fat theory

Under the right circumstances, any kind of movement or fiction can begin to generate static electricity that builds up on a person’s body or the objects around them. Occasionally this electricity is enough to generate a spark that ignites a fine fabric or lint.

If the circumstances are right, and the person is unable to react in time, the burned fabric can generate a kind of “chain reaction” in which new fabrics are ignited in turn. Eventually, a considerable part of the clothing may be incinerated.

It is natural for a person to react in time to take off his or her clothes, jump into water or at least roll on the ground. However, if the person is unconscious or unable to react, a second phase may occur which, although possible, is very unlikely: before the clothing is completely burned, through wounds or burns on the skin, subcutaneous fat may start to flow and soak the burning tissues.

And then the process works. Like the pistil of a candle, which can burn for hours without being burned by the rising wax, the fat-soaked tissue will burn until all the fat is gone – which can represent several hours on average for one person – causing the other tissues to carbonize in the process. Although the temperature may not get that high, it is the duration of the flame that creates the peculiar result.

Some years ago several experiments were conducted on pig carcasses in which the flame burned for up to 8 hours and reached temperatures of up to 800°C. The “clothed” parts of the pigs disappeared completely, while the uncovered parts, not having a flame-providing fabric, were preserved without more than superficial burns. This proved that, at least in theory, this type of burns can happen.

The theory of metabolism

Some go beyond the aforementioned theory and claim that human beings can not only burn, but that they can be the generators of fire themselves. Thus, the human body would be a machine capable of catching fire at any time regardless of external conditions.

As we know, our body stores energy in the form of glucose, fat and – at the cellular level – ATP. These are all highly flammable compounds that the body manipulates in tiny amounts to obtain the energy needed to live. In a way, our cells are miniature power plants that get their energy from the oxidation (which is just another word for “burning”) of glucose.

It is easy to assume that, under exceptional circumstances, the brakes on the system could fail and the body temperature could rise to the flash point. Thus, this miniature combustion that occurs specifically when the cell requires it could, for unknown reasons, begin to occur en masse, rapidly causing the system to overheat leading to the ignition of entire sugar or fat-based tissues.

Thus, the person would burn “from the inside”, causing within seconds their body to increase in temperature in localized locations leading to death. The continuation of the flames could then do its part and turn the victim’s body into ashes.

The baby in India allegedly suffering from spontaneous combustion

Some specific cases seem to point more to this type of HEC than the other. However, this theory has not been proven and so far is not supported by the available evidence. One of the emblematic cases – that of a baby less than one year old in India – aroused the suspicions of physicians, who believe that it is not an abnormal event but simply and simply mistreatment.

Spontaneous combustion is a phenomenon in which a material begins to burn without an obvious external heat source. This process has been the subject of myths and legends throughout history, but it is a real phenomenon that occurs with some regularity in everyday life and in some industrial processes.

One of the best known examples of spontaneous combustion is that of hay and straw stacks. These materials, which contain a large amount of dry plant material, are prone to spontaneous combustion when stacked in large quantities and subjected to certain environmental conditions, such as humidity, heat and lack of ventilation.

Another common example is the spontaneous combustion of oils and fats. When oils and greases oxidize with air, they release heat and can reach temperatures high enough to ignite. This phenomenon is especially dangerous in the food industry, where the accumulation of oils and fats in kitchen exhaust hoods can cause fires.

Spontaneous combustion can also occur in some organic materials, such as wood, paper and cotton, which contain substances that oxidize in air. When these materials are exposed to the right temperature and humidity, oxidation can accelerate and cause spontaneous combustion.

In the case of humans, cases of human spontaneous combustion have been reported, but this phenomenon is extremely rare and its explanation has not yet been fully elucidated by science. The cases that have been reported usually involve elderly and obese people who smoke and drink heavily and who have been found in their home completely charred without evidence that a fire was started by an external source.

At the molecular level, spontaneous combustion occurs when a substance oxidizes and releases heat energy, which can start an oxidation chain reaction that releases even more heat. If the temperature increases sufficiently, complete combustion can occur, which means that the substance burns completely and releases gases such as carbon dioxide and water vapor.

In some cases, spontaneous combustion can be difficult to detect as it does not always produce a visible flame. For example, in the case of hay and straw piles, the material may begin to burn slowly inside, producing thick smoke and a large amount of heat before a visible flame is observed on the surface.

Prevention of spontaneous combustion involves a proactive approach to identifying and controlling hazards in combustible materials. This may include the use of temperature monitoring and analysis techniques, proper ventilation of materials, maintaining proper temperature and humidity, and adopting safe storage and handling procedures for materials.

In industry, companies can implement fire safety and prevention plans, as well as train workers on the risks of spontaneous combustion and how to prevent it. In the home, it is important to follow safety instructions when storing and handling combustible materials, such as flammable liquids, aerosols and chemicals.

Although spontaneous combustion has been documented and studied for centuries, there are still many unanswered questions about how and why it occurs. In the case of humans, for example, several theories have been proposed to explain the rare cases of human spontaneous combustion, including the accumulation of flammable gases in the body and the chemical reaction of body fats. However, none of these theories have been completely proven by science.

In addition, spontaneous combustion can also be influenced by external factors, such as exposure to ionizing radiation and electromagnetic fields. In some cases, spontaneous combustion of materials has been reported in the vicinity of high-voltage pylons and other electrical devices.

On the other hand, spontaneous combustion has also been investigated in the field of renewable energy, in particular in the spontaneous combustion of biomass and organic wastes. These materials, which are used as fuels in power plants and incineration plants, can undergo spontaneous combustion due to the accumulation of flammable gases and the presence of heat-producing bacteria.

Spontaneous combustion can also occur in fatty foods, oils and other flammable liquids. For example, if hot oil is left in a frying pan for too long, it can reach a critical temperature and start to burn spontaneously. Likewise, the accumulation of flammable gases inside a fuel tank can also cause spontaneous combustion if a spark occurs.

In the industrial environment, spontaneous combustion can be a risk in the handling and storage of chemicals, organic and other combustible materials. Therefore, it is important that workers are trained in safety and fire prevention measures, and that adequate safety protocols are adopted to minimize risks.

In the agricultural industry, spontaneous combustion is a common risk in hay and straw production. These materials may contain bacteria that decompose organic matter and produce heat as a by-product. If the temperature is not properly controlled, heat buildup can cause spontaneous combustion within the hay or straw pile.

In science, spontaneous combustion is also the subject of study in physics and chemistry. Theoretical models and experiments have been developed to understand the mechanisms underlying spontaneous combustion, leading to advances in the design of fire-resistant materials and fire prevention.

In physics, heat and mass transfer processes have been studied in systems in which spontaneous combustion occurs. Theoretical models and experiments have provided insight into how heat transfer and the release of thermal energy can lead to a chain reaction that triggers spontaneous combustion.

In chemistry, the oxidation and chemical decomposition processes that occur in materials that can undergo spontaneous combustion have been investigated. Specific chemical compounds that can trigger spontaneous combustion have been identified and techniques have been developed to prevent their formation.

In the engineering field, techniques have been developed to prevent spontaneous combustion in storage and transport systems for combustible materials. Fire resistant materials and fire detection and extinguishing systems have been designed to minimize risks.