Tires are complex, highly durable products primarily composed of synthetic and natural rubber, carbon black, and petroleum-based oils, all of which contribute to their high energy content. When ignited, these materials create a unique and extremely difficult fire scenario that can persist for surprisingly long periods. The duration of a tire fire is highly unpredictable because the structure designed for road resilience—its density and insulating properties—also allows a fire to smolder and sustain itself. The time a tire burns can range from a few minutes for a single tire to weeks or even months for a massive scrap pile, making the event duration highly dependent on surrounding variables.
The Chemistry of Tire Combustion
A typical tire consists of approximately 60% rubber polymers, a mixture of natural and synthetic rubber, and about 30% reinforcing carbon black and various oils. The remaining mass includes steel belts and fabric cords, all of which contribute to the tire’s dense, hydrocarbon-rich structure. This composition is what gives tires a high calorific value, making them comparable to coal as a fuel source. The burning process is often sustained by a mechanism called pyrolysis, which is the thermal decomposition of organic material in the absence of oxygen. The high heat from the initial combustion breaks down the solid rubber into flammable gases and a hazardous liquid known as pyrolytic oil. These newly created gases, such as methane and various hydrocarbons, then fuel the visible flames, while the remaining solid material continues to decompose. This cycle makes tire fires difficult to extinguish, as the fire is essentially generating its own fuel source beneath the surface.
Variables Influencing Burn Duration
The single most significant factor controlling how long a tire fire lasts is the availability of oxygen to the burning material. In large, densely packed stockpiles, the physical arrangement of the tires severely limits the amount of air that can reach the deep-seated core of the fire. This lack of oxygen slows the flaming combustion, but it allows the high temperatures to be maintained, resulting in a prolonged, smoldering pyrolysis rather than a fast, clean burn.
The density of the stacking is important, as tightly packed piles burn slower but for a much longer duration due to this self-insulation effect. The rubber itself is a poor conductor of heat, which means the heat generated by the fire remains trapped within the pile, preventing heat loss and sustaining the high-temperature breakdown of the material. This sustained, internal heat is what allows massive tire fires to persist for weeks or even months.
The size and type of tire also play a role in the duration of the burn. A large truck or construction tire contains far more mass and is thicker than a small passenger car tire, supplying a greater volume of fuel for the fire. The sheer volume of material in a massive scrap tire pile, which can number in the millions of tires, is the ultimate determinant of a prolonged burn. Furthermore, the internal steel belts can reach high temperatures and re-ignite the fire even after the visible flames have been suppressed.
Typical Burn Times Based on Fire Scale
The duration of a tire fire is best understood by examining the scale of the incident, which directly correlates to the total fuel load and oxygen access. A single passenger vehicle tire exposed to an external heat source will typically burn for a relatively short time, often ranging from 15 minutes to an hour before the bulk of the rubber is consumed. The fire behavior in this scenario is generally a quick, flaming combustion until the available material is spent.
A small pile of tires, such as those involved in a vehicle fire or a roadside dump, may burn for several hours to a full day. Once the fire involves a larger number of tires, the insulating properties of the rubber and the pile density begin to trap heat, necessitating more aggressive suppression tactics.
In contrast, massive scrap pile fires, containing millions of tires, can become deeply entrenched, low-oxygen pyrolysis events that defy traditional firefighting methods. These immense fires can burn for weeks, months, or in extreme cases, require over two years to fully extinguish through a combination of water, foam, and smothering the material with dirt or sand to cut off the oxygen supply.
Immediate Environmental Byproducts
The combustion of tires immediately releases a dense, black smoke plume that is highly visible and travels great distances from the source. This smoke is a complex mixture of gases and particulate matter, including a high concentration of sulfur oxides, carbon monoxide, and volatile organic compounds (VOCs). The smoke also carries heavy metals, such as zinc, cadmium, and chromium, which were incorporated into the tire during the manufacturing process.
A significant concern is the generation of pyrolytic oil, a hazardous liquid byproduct of the thermal breakdown of the rubber. As the tires melt, this petroleum-based oil runs off the burning material and can contaminate the surrounding soil and surface water. The Environmental Protection Agency (EPA) estimates that for every one million tires consumed by fire, approximately 55,000 gallons of this toxic runoff oil can be released into the environment. This oily residue contains polycyclic aromatic hydrocarbons (PAHs) and other petroleum hydrocarbons that pose a substantial risk to groundwater and local ecosystems.