The question of whether fingernails are flammable often sparks curiosity. Understanding their behavior under high temperatures involves examining their unique composition and how it interacts with heat. This exploration distinguishes their reaction from that of more readily combustible substances.
The Composition of Finger Tissue
Fingernails are primarily composed of a fibrous protein known as alpha-keratin. This same protein is a major component of hair, the outer layer of skin, and various animal structures like claws, hooves, and horns. The visible part of the nail, called the nail plate, consists of multiple layers of dead, densely compacted keratin cells, contributing to its strength and resilience. Unlike many other organic materials, keratin is highly insoluble in water and organic solvents, which contributes to its durability.
The tightly packed and cross-linked structure of keratin proteins provides fingernails with their characteristic hardness and resistance to combustion. Fingernails contain minimal amounts of lipids (less than 5%) and water (7% to 18%), meaning few volatile or easily ignitable compounds are present. The presence of sulfur, a notable component in keratin, plays a role in its flame-retardant properties. This unique biochemical makeup sets fingernails apart from materials like wood or paper, which contain more readily flammable compounds.
How Finger Tissue Responds to Heat
When fingernails are exposed to an open flame or intense heat, they do not ignite rapidly or burst into sustained flames like many other organic substances. Instead, the reaction is charring, curling, and slow decomposition. High temperatures cause the keratin proteins within the nail to denature and break down. This decomposition releases various gases, including ammonia and carbon dioxide, leading to a distinct odor similar to burning hair.
While fingernails are technically combustible at very high temperatures, they do not readily ignite under normal conditions. If held directly in a flame, they burn very slowly, forming a blackened char rather than supporting a spreading fire. This behavior is due to the self-extinguishing properties of keratinous fibers, which contain amino acid groups rich in nitrogen and sulfur compounds that help inhibit flame propagation. Once the heat source is removed, fingernails cease burning, demonstrating their limited flammability. Artificial nails, made from synthetic polymers, can readily catch fire and cause severe burns upon exposure to a flame, a stark contrast to natural fingernails.
General Fire Safety
While fingernails themselves are not highly flammable, direct exposure to fire remains dangerous and can cause severe burns to the surrounding skin and underlying tissues. The heat from any flame can quickly injure the sensitive living tissue beneath and around the nail, leading to pain and potential long-term damage. It is important to prioritize general fire safety practices to protect oneself and others from fire hazards.
Simple precautions can reduce the risk of fire-related incidents. Installing and regularly testing smoke alarms on every level of a home provides early warning in case of a fire. Developing and practicing a fire escape plan with multiple escape routes is essential for all household members. Exercising caution around potential fire sources, such as never leaving cooking unattended, keeping space heaters at a safe distance from flammable objects, and extinguishing candles before leaving a room or going to bed, can prevent accidents.