In this paper, an attempt has been made to optimize the combustion air (secondary air) injection to the combustion chamber of a cookstove which in turn provides a better fuel burning rate and firepower. The optimization of the injection angle of the combustion air profile is done through simulation analysis using computational fluid dynamics (CFD) ANSYS FLUENT 14.0 software. The obtained velocity gradient result demonstrates a uniform spread of velocity with the higher magnitude in the combustion chamber between the gasification and combustion air inlet at an injection angle of 45°. The water boiling test (WBT 4.2.3) protocol was used as a testing procedure for the evaluation of cookstove performance. The thermal energy efficiencies obtained for the new cookstove are 36.7 ± 0.4%, 37 ± 0.4% and 38 ± 0.4%, and the exergy efficiencies are 15.6 ± 0.5%, 17.5 ± 0.5% and 15 ± 0.5% for coconut shells, Prosopis juliflora and tamarind seed pellets, respectively. Flame propagation rate, fuel burning rate and particulate matter (PM 2.5 ) emission are the measured values used for estimating the combustion characteristics and indoor air quality for different fuels. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.