The effect of oxygen content and of the combustion air velocity on soot formation was studied in acetylene diffusion flames. These flames were produced in a burner with a parallel annular coaxial flow of oxidizer. The effect on the flame axial temperature profile was also evaluated. The soot volume fraction was calculated by the laser light extinction methodology. The oxygen content in the combustion air was smaller than 30%, which does not require significant retrofit of existent equipment when the combustion conditions are varied. The results suggest that the parallel manipulation of the oxygen content and of the oxidizer velocity can provide means for managing soot formation and distribution. The formation of soot in industrial combustion systems is of interest in engineering, because the presence of soot in the flame enhances the heat transfer from the combustion gases by thermal radiation, increases the need for burner maintenance, and constitutes an environmental problem when emitted in the atmosphere. (C) 2009 Elsevier Ltd. All rights reserved.365445450