The thermal destruction of perfluoroalkyl substances (PFAS) has garnered much attention recently due to concerns of adverse health effects, environmental bioaccumulation, and long half-lives. Full mineralization of all C-F bonds into HF and CO 2 is necessary for effective removal of PFAS from contaminated matrices, but the combustion is often incomplete. The difficulty in experimentally characterizing the products of incomplete combustion, which are potentially hazardous, has prompted a variety of computational studies into the chemical reaction mechanisms of PFAS pyrolysis and oxidation. Extensive examinations of the thermochemistry of species involved in the destruction of perfluorinated carboxylic acids and perfluorinated sulfonic acids indicate that radical-radical reaction channels, such as homolytic dissociation within perfluoroalkyl chains, are likely important alongside molecular or pericyclic reactions with sufficiently low electronic barriers to contribute at incineration conditions. However, in the existing theoretical studies on PFAS thermal decomposition, the consideration of barrierless reactions has been limited.