Fire is a rapid, self-sustaining oxidation process accompanied by the emission of heat and light. For fire to occur, three elements are required: heat, fuel, and oxygen. The question of whether humans can catch fire relates to whether the human body can provide the fuel and conditions necessary for combustion to occur.
Can the human body burn?
The human body is composed primarily of water, fat, and protein. While the fat and protein components can burn under certain conditions, the high water content of the body makes it difficult for the body to ignite and sustain fire.
Human fat can serve as a fuel source for fire. Body fat generally burns at temperatures between 250°C and 300°C. However, fat on the human body is stored in adipose tissue below the skin, so an external heat source of high temperature would need to be applied to melt the fat and raise it to its ignition temperature. This fat layer also provides some insulation against heat transfer.
Skin, hair, and other protein-rich tissues of the body can burn once heated to high temperatures. However, proteins require even higher temperatures to combust, typically above 300°C. The water content of these tissues makes reaching these temperatures difficult.
The high water content of the human body is the primary impediment to the body catching fire. Water has a very high specific heat capacity, meaning it requires a lot of energy to raise its temperature. Water makes up 50-75% of the body by mass, so heating the water content of tissues would require enormous amounts of external heat. Additionally, the evaporation of water cools the body as heat is absorbed.
Under what conditions can the human body catch fire?
While the human body is not prone to igniting, there are extreme circumstances under which a human can catch fire:
- Exposure to an external heat source of over 300°C. This could come from something like direct contact with flames or very hot surfaces.
- Being in an oxygen-rich environment. More abundant oxygen can make combustion processes more rapid.
- Having flammable, fuel-rich surroundings. For example, being covered in or soaked with accelerants like gasoline or alcohol can essentially turn the body into a wick.
- Having dry skin and clothing. Having very low moisture content eliminates a retardant to ignition.
- Hair burning and igniting other parts of the body. Hair can burn more readily and spread fire to clothing and skin.
Some real-world examples demonstrate the conditions needed for a person to catch fire:
- Pilots or race car drivers catching fire after a crash where fuel leaks out and ignites.
- A person caught in a burning room or wildfire becoming engulfed in flames.
- A person doused with accelerant and intentionally set alight.
- A person exposed to extreme heat from a burner or industrial accident that causes clothing or hair to catch fire first.
In these types of situations, there is an external fuel source and heat levels high enough to ignite clothing, hair, or skin. The body itself serves as additional fuel to keep the fire spreading.
How does the body burn?
When the human body does catch fire, the order in which different tissues burn is fairly consistent:
- First, any clothing on the body ignites.
- If hair is exposed, it can begin to burn next.
- The fat layer below the dermis of the skin melts and combusts.
- Finally, the muscle and other protein-rich deep tissues will burn if temperatures are sustained.
Studies have measured the temperatures and length of exposure needed to incur various degrees of burn injuries:
| Burn Degree | Skin Temperature | Time for Injury |
|---|---|---|
| First-degree | 44°C | 5-10 seconds |
| Second-degree | 60°C | 1 second |
| Third-degree | 75°C | 1 second |
As evidenced by this table, direct flame exposure, generating temperatures over 75°C, can immediately destroy skin. More prolonged heat exposure leads to burning of subcutaneous fat and muscles.
Role of clothing
Clothing plays a major role in the way burns progress on the body. Most clothing materials can ignite at temperatures between 400-700°C, much lower than what is required to ignite skin or tissues. As clothing catches fire, it can adhere to the skin and transfer heat rapidly, resulting in severe burns.
Clothing may also be fuel-soaked, especially for burns involving gasoline or similar liquids. Having this flammable fuel source in direct contact with the body allows for fire to establish and spread across the skin’s surface even without high ambient temperatures.
Injuries from burns
Burns that cover large portions of the body result in immense physiological stresses. Major life-threatening complications include:
- Fluid loss – Plasma and water leaks rapidly from burned tissues.
- Infection – Destroyed skin loses its barrier function, allowing pathogens entry.
- Impaired temperature regulation – Skin damage reduces ability to sweat and retain heat.
- Respiratory changes – Swelling and fluid buildup can restrict breathing.
If a burn victim survives the initial trauma, the long process of debriding, skin grafting, and rehabilitation begins. Disfigurement is highly likely. Overall, the prognosis depends on the total body surface area burned and any pre-existing conditions of the individual.
Fire-related deaths
Fire represents a major cause of injury and death worldwide. The WHO estimated over 180,000 fire-related deaths occurred globally in 2002 alone. Fire deaths disproportionately affect poorer countries and younger children.
Fire can kill through several mechanisms:
- Burns – Both thermal damage and physiological effects.
- Asphyxiation – Smoke inhalation prevents oxygen uptake.
- Toxic gases – Carbon monoxide and other products of incomplete combustion.
- Trauma – Jumping from buildings, burns weakening structures leading to collapse.
Smoke inhalation and poisoning along with burns are estimated to account for most fire deaths. As little as 3 breaths of superheated air at 200°C can render a person unconscious. Any burns incurred after falling unconscious are especially dangerous since the victim cannot escape.
Burn statistics
In the United States, approximately 400,000 burn injuries require medical treatment each year. Of those injuries:
- 25% are in children under age 16
- 50,000 result in hospitalization
- 3,400 lead to death
Scalding from hot liquids, explosions and flash burns from fuels, and direct flame contact represent the most common causes. Proper safety precautions and fireproofing of buildings and materials can help reduce risk.
Case studies
Michael Jackson Pepsi commercial accident
While filming a Pepsi commercial in 1984, Michael Jackson’s hair caught fire from pyrotechnics effects gone wrong. Jackson suffered second and third-degree burns to his scalp and body which required hospitalization and reconstructive surgeries. This began Jackson’s long-term use of painkillers which may have contributed to his eventual death by overdose.
Budd Dwyer public suicide
Former Pennsylvania state treasurer Budd Dwyer committed suicide at a televised press conference in 1987. After proclaiming his innocence on corruption charges, he drew a pistol and shot himself in the mouth. The gunshot did not immediately kill him, and his hair and head caught fire from the gun’s discharge smoke and gasses. He fell to the floor convulsing and burned for several seconds before aides could extinguish the flames.
Conclusion
While the living human body has safety mechanisms that make successfully igniting it difficult, under extreme conditions the body can sustain burns. Typically an external heat source is needed to pre-heat clothing, hair, or surrounding air to temperatures exceeding 500°C before skin or tissues will ignite and continue burning. However, even minor burns that char the skin can lead to severe trauma and death if large portions of the body are affected. Fire prevention and safety remains vitally important to prevent both fire-related injuries and unintentional burning of human bodies.