Method to produce a product gas with low tar and dust contents from solid biomass, biogenic residues and/or organic waste fractions with a gas production device, the gas production device comprising: a fuel conversion reactor (1a, 1b), which is an updraft gasification reactor or a pyrolysis reactor; and a gas treatment reactor located downstream the fuel conversion reactor (1a, 1b); wherein the fuel conversion reactor (1a, 1b) is directly connected with the gas treatment reactor; wherein the fuel conversion reactor (1a, 1b) comprises a space to contain a fuel bed above a grate; wherein the gas treatment reactor comprises the following: a POX zone, and at least one POX nozzle for supplying an oxidiser into the POX zone; and a gas heating zone fluidic located between the space to contain the fuel bed and the POX zone; a heat exchanger section (11, 14) for the gas heating zone; wherein the method comprises the following steps: Creating an initial product gas in the fuel conversion reactor (1a, 1b); Heating the initial product gas, which is created in the fuel conversion reactor (1a, 1b), in the gas heating zone before it enters the POX zone, by the heat exchanger section (11, 14) by at least 150°C; Combusting the heated initial product gas in the gas treatment reactor partially in the POX zone of the gas treatment reactor by injecting or supplying an oxidiser through the POX nozzles into the POX zone. a fuel conversion reactor (1a, 1b), which is an updraft gasification reactor or a pyrolysis reactor; and a gas treatment reactor located downstream the fuel conversion reactor (1a, 1b); wherein the fuel conversion reactor (1a, 1b) is directly connected with the gas treatment reactor; wherein the fuel conversion reactor (1a, 1b) comprises a space to contain a fuel bed above a grate; wherein the gas treatment reactor comprises the following: a POX zone, and at least one POX nozzle for supplying an oxidiser into the POX zone; and a gas heating zone fluidic located between the space to contain the fuel bed and the POX zone; a heat exchanger section (11, 14) for the gas heating zone; a POX zone, and at least one POX nozzle for supplying an oxidiser into the POX zone; and a gas heating zone fluidic located between the space to contain the fuel bed and the POX zone; a heat exchanger section (11, 14) for the gas heating zone; wherein the method comprises the following steps: Creating an initial product gas in the fuel conversion reactor (1a, 1b); Heating the initial product gas, which is created in the fuel conversion reactor (1a, 1b), in the gas heating zone before it enters the POX zone, by the heat exchanger section (11, 14) by at least 150°C; Combusting the heated initial product gas in the gas treatment reactor partially in the POX zone of the gas treatment reactor by injecting or supplying an oxidiser through the POX nozzles into the POX zone. Creating an initial product gas in the fuel conversion reactor (1a, 1b); Heating the initial product gas, which is created in the fuel conversion reactor (1a, 1b), in the gas heating zone before it enters the POX zone, by the heat exchanger section (11, 14) by at least 150°C; Combusting the heated initial product gas in the gas treatment reactor partially in the POX zone of the gas treatment reactor by injecting or supplying an oxidiser through the POX nozzles into the POX zone.