Pseudo-Elementary Reaction Kinetics (PERK) mechanisms are developed to keep the size of the mechanism small while enabling the ability to capture a broader range of conditions than with models containing global reaction steps. While the pre-reduced mechanisms (see MFL Pre-Reduced Mechanisms) preserve the accuracy of detailed mechanisms to a great extent, PERK mechanisms are designed to forgo some of that accuracy and maintain a compact size of a component mechanism.

PERK mechanisms are constructed by considering only dominant reaction pathways for fuel reactions among many that are found in a detailed mechanism. Reactions are formulated to omit intermediate species, therefore resulting in products involving several small species. Rate constants for these reactions are optimized to match predictions of the detailed mechanisms. Elementary reactions of methane and hydrogen from the MFL are used without modification as the core chemistry in all PERK mechanisms.