This chapter describes the chemical and physical properties associated with thermal destruction. It also describes heat and mass transport in the incinerator. The chapter explains how to apply basic concepts of chemical kinetics, equilibrium, stoichiometry and thermochemistry to the design of thermal processes. It provides a discussion on a design approach for thermal processes design and technologies used for control of air pollution. Thermal destruction processes involve many complex interactions. The following disciplines govern the thermal destruction process: thermodynamics, chemical kinetics, heat and mass transfer, and fluid mechanics. This complex relationship is further complicated by shifts in waste composition, resulting in changes in heat release rate and combustion characteristics. Waste characterization is a major factor in assessing the feasibility of destroying a hazardous waste by thermal destruction processes. The design of the process and the air emissions control system are determined by the waste characteristics.