The flow velocity measurements and flux measurements of gas species of O2, CO2and NO in an oil furnace were carried out. The velocity profiles in combustion and noncombustion were measured by the developed LDV, and the results show that the reversing flow regions for both cases were located at the same place and their volumes were almost equal. The comparisons of measured concentration and flux obtained using velocity and temperature were performed in spray combustion. The results show that there is little difference in the flame region but a large discrepancy outside of the flame region. The generated gas species in the flame and its convection outside of the flame were discretized, and the application of flux in spray combustion research was found to be very useful and effective. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.