Scientifically, the flammability of any substance, including human blood, is determined by its chemical composition and physical state. Fresh, liquid blood is overwhelmingly resistant to combustion under normal conditions. However, once the liquid component is removed, the remaining solids present a different, yet still complex, set of chemical properties.
What Makes Something Flammable?
Flammability, the ability of a substance to ignite or sustain combustion, requires the simultaneous presence of three elements: fuel, oxygen, and heat. Fuel is the material that burns, oxygen is typically from the surrounding air, and heat must be sufficient to raise the fuel to its ignition temperature. The ignition temperature is the minimum temperature at which a substance produces enough flammable vapor to ignite. If any one of these three components is removed, the combustion reaction cannot start or be sustained. Highly flammable substances readily vaporize or decompose into ignitable gases at low temperatures.
The Role of Water in Fresh Blood
Fresh, liquid blood is overwhelmingly non-flammable. Water makes up approximately 80% to 85% of its total volume, and the liquid component, plasma, is nearly 90% water itself. Water acts as a powerful thermal inhibitor, as it absorbs a tremendous amount of heat energy before its temperature rises.
For the organic solids in the blood to reach their ignition point, all of this water must first be converted into steam. This process of vaporization actively cools the remaining material, preventing it from reaching the necessary temperature for combustion. The energy required to boil off the massive water content is far greater than the energy supplied by typical ignition sources. A simple match will only cause the fresh blood to steam and dry out, not burst into sustained flames.
Ignition Potential of Desiccated Blood
When all the water evaporates, the remaining substance is desiccated blood, a collection of organic and inorganic solids. This dry matter is composed primarily of proteins, such as hemoglobin and albumin, along with carbohydrates and various mineral salts. The organic matter represents the potential fuel source, as these are carbon-based compounds.
However, the high concentration of inorganic components acts as a natural flame retardant. Dried blood contains a significant ash content, which is the mineral residue left after combustion. This ash consists of non-combustible inorganic salts, including sodium and potassium chlorides, which do not contribute to the fire.
Furthermore, the iron atoms found within the hemoglobin molecules are also non-combustible and can interfere with the oxidation process required for sustained burning. While the organic proteins can char or smolder under extreme and prolonged heat exposure, the high mineral content makes true, sustained flaming combustion highly improbable. Desiccated blood is difficult to ignite and is generally self-extinguishing once the direct heat source is removed.