The transport of heat and species generated by the chemical reactions is an essential aspect of most combustion processes. These transport processes can be described by the conservation equations commonly used in fluid and heat transfer analysis of engineering problems. Additional terms in the mass, momentum, and energy conservation equations account for the effects of the chemical reactions. This chapter briefly discusses heat and mass transfer, the equations governing combustion systems (conservation of mass, species, momentum, and energy), the normalization of the conservation equations, and simple expressions for the variation of viscosity, conductivity and diffusivity.