Butanol is thought to be a promising alternative biofuel for fossil fuels, which has four different isomers, i.e., 1-butanol, 2-butanol, iso-butanol and tert-butanol. Detailed kinetic analysis of H-2 effects on laminar rich premixed flames of these four butanol isomers are performed at atmospheric pressure and the H-2 chemical effects are emphasized. The detailed chemical mechanism for high-temperature oxidation and combustion of butanol isomers developed by Sarathy et al. [Combust Flame 2012;159:2028-55] which consists of 286 species and 1892 reactions was used in this study. The equivalence ratios for all the flames are kept constant to be 1.5. The chemical effects of H-2 additions on the four butanol isomers flames are separated from the H-2 dilution and thermal effects. The effects of H-2 addition on major species, intermediate stable species and radicals are analyzed and compared in details for different butanol flames. The rates of production of acetylene, formaldehyde, acetaldehyde, and key radicals are given to obtain the responsible reactions during the butanol combustion with and without H-2 additions. In addition, the pathway analyses for these flames are presented and discussed. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.