Combustion process in a furnace comprising a floor on which a charge to be heated is placed, and a roof lying above the charge, in which process the combustible fluid and the oxidizer fluid are injected separately between the surface of the charge and the roof, characterized in that the oxidizer and the fuel are injected at two different levels and in that the ratio of the impulsive forces (m.sub.2.v.sub.2 /m.sub.1.v.sub.1) of the combustible and oxidizer fluids is greater than or equal to approximately 1/3, m.sub.1 being the mass flow rate of the top fluid and v.sub.1, its velocity of injection into the furnace, m.sub.2 being the mass flow rate of the bottom fluid and v.sub.2 its velocity of injection into the furnace.