The Particle Tracking feature provides an efficient numerical method for predicting particle formation and for tracking the evolution of particle size distributions in a reacting-flow simulation. This utility is built on proven technologies such as Ansys Chemkin's Surface Kinetics capabilities and the method of moments reported by Frenklach et al.[156], [157], [158] The innovation of the Particle Tracking module resides in the treatment of particle inception, growth, and reduction processes. By expressing particle inception, growth, and reduction processes in terms of surface reactions, the user has full control over the particle growth kinetics. This implementation greatly simplifies the postulation and testing of different precursors and growth or consumption paths.