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LEA Advisory #46 - Evaluation of Employee Health Risk from Open Tire Burning Page 2 of 8 <br /> synthetic fibers, pigments, processing chemicals, and steel or fiberglass. Tire manufacturers use a <br /> variety of formulation recipes when producing tires. For specific information on the processing and <br /> manufacturing of tires refer to the Board's report Effects of Waste Tires, Waste Tire Facilities, and <br /> Waste Tire Projects on the Environment. The following table lists a typical tire composition. <br /> Typical Tire Composition: Passenger Tire Recipe <br /> Material Percentage <br /> Styrene 46.78% <br /> butadiene <br /> Carbon black 45.49% <br /> Aromatic oil 1.74% <br /> Zinc oxide 1.40% <br /> Stearic acid .94% <br /> Antioxidant 6C 1.40% <br /> Wax 0.23% <br /> Sulfur 1.17% <br /> Accelerator CZ IF <br /> 0.75% <br /> An automobile tire weighs about 20 pounds, with a diameter ranging from 18-30 inches. In addition <br /> to rubber, a tire contains some steel in the bead and some rayon or steel in the belt. An average tire is <br /> produced from about 2.5 gallons of petroleum, making it a good source of heat energy. Shredded or <br /> chipped tires, without their steel belts, have an energy content ranging from 14,000 to 15,000 Btu per <br /> pound. Coal has an energy content of 8,000 to 12,000 Btu per pound. <br /> Process <br /> When tires are burned, the rank smell can probably be attributed to sulfur-bearing compounds. The <br /> carbon black used in the vulcanization of rubber is the source of most of the dark particulate matter. <br /> "As a tire burns, two distinct types of burning appear to occur, during which emissions will differ. <br /> These burn patterns correspond to the materials in the tread layers and the belt layers of the tires." <br /> (CTC,1989, page 3) Tire combustion occurs at a temperature range of approximately 100 (remote <br /> from the flame) to 2000 (at the flame front) degrees centigrade (° Q. Ideal burn conditions would <br /> include adequate time for mixing of fuel and air, high temperatures, and complete mixing between <br /> the fuel and air. The fire burn rate can be affected by the material size. Shredded tires will burn at a <br /> much lower rate than chunk tires. Small-scale simulation of open burning of tires found the gaps <br /> between the tire material provides a pathway for oxygen transport and appears to be the controlling <br /> mechanism for sustaining the combustion process. <br /> http://www.ciwmb.ca.gov/pe/advisory/46/46.htm 8/11/98 <br />