Abstract: A method of inhibiting formation of unburned substances in incinerating refuse is practiced with use of an incinerator wherein a peripheral wall defining a combustion chamber is provided with a nozzle for injecting at least one mixing fluid selected from the group consisting of air, water, water vapor, inert gas and combustion exhaust gas into the combustion chamber and producing a swirling stream of the fluid within the chamber. When the refuse is incinerated, the mixing fluid is injected into the combustion chamber from the nozzle, whereby the flame and unburned substances produced within the chamber are efficiently mixed with an excessive portion of air supplied to the chamber and remaining therein to ensure promoted complete combustion.