(a) should tyres catch alight, each tyre can emit around two litres of oil during combustion, thereby serving to increase the fire risk and the spread of any fire;
(b) if stacked tyres catch alight, the lower combusting tyres are compressed. This will result in tyres higher up the stack moving deeper into the stack, and therefore, into the heat of the combustion zone. In tyre stacks that are vertical a "chimney effect" may occur. This causes air to be drawn in from the bottom (one side) of the tyre and travel upwards via the combustion zone. This encourages the flaming combustion to stay inside the tyre. Additionally, combusting tyres can roll off the stack and spread fire to other stacks if tyres are stored "tread-up";
(c) even after flaming combustion ceases, the smouldering may continue for a long period. During the smouldering phase, combustion by-products continue to be emitted by the tyres;
(d) the fire dynamics associated with a burning stack of tyres maintains the flaming combustion on the inside of the tyres. This makes it hard, if not impossible, for firefighting extinguishing agents to reach the combustion zone, especially if the stack is tall. Therefore, the outcome often is an excessive amount of firefighting water discharged at the fires;
(e) as excessive amounts of firefighting water is discharged onto tyre fires, this results in large amounts of fire water runoff, which needs to be managed. Atmospheric emissions include carbon monoxide, sulphur oxides, nitrogen oxides, volatile organic compounds, cyclic aromatic hydrocarbons, hydrogen chloride, benzene, and polychlorinated biphenyls. Liquid emissions are mainly an oil or hydrocarbon substance, which can adversely impact water ways. This oily by-product contains several other substances including, naphthalene, benzene, anthracene, sulphur compounds, arsenic, and cyanide; and
(f) there are various available ignition sources for tyre fires to occur at facilities such as the premises. In waste or recycling tyre facilities, tyre fire ignition causes are generally arson, bush or grass fires, on-site machinery fires, and lightning strikes.