This paper presents analysis of pine and sunflower husk pellet combustion and their co-combustion with oats in a domestic biomass boiler. Selected physical and chemical properties of the studied biomass pellets were determined. Thermal analysis (TGA) of the analyzed biomass in air atmosphere was carried out. The concentrations of CO, CO2, NO and NO2 in the exhaust gases were also examined. The obtained experiment results were compared with the numerical calculations using CHEMKIN-PRO. The best convergence of the experiment results with the calculations was obtained for a residence time of 2 s and temperature of 650 degrees C. The experiment and calculated results show that the co-combustion of pellets with oats contributes to reducing the CO and CO2 concentrations in the flue gas.(c) 2020 Elsevier Ltd. All rights reserved.