Detailed measurements within sprays are needed to understand the vaporization, transport, and combustion of liquid fuels. While diagnostics have been developed to characterize the structure of the spray droplets in great detail (e.g., phase Doppler interferometry), details regarding the gas phase (e.g., oxidizing media and fuel vapor) are more difficult to obtain. In the present study, measurement of gas phase vector properties are achieved in the spray field of a twin-fluid atomizer using phase Doppler interferometry. A gas phase scalar, the concentration of hydrocarbon vapor, is measured using an infrared extinction/scattering technique. When combined, the two measurements provide a direct measure of the vaporization characteristics of the spray. A methanol spray is studied which is produced by an atomizer operating at three conditions, (1) no atomizing air, (2) non-swirling atomizing air, and (3) swirling atomizing air. The injection mode alters the vaporization behavior of the spray. For the non-reacting cases, (1) the presence of non-swirling air-assist, while not strongly affecting the spatial vaporization history, enhances the temporal vaporization rate compared to the case without atomizing air; (2) the presence of swirling atomizing air greatly enhances the vaporization rate in both space and time; and (3) examination of the rate of change of vaporization reveals a correlation among all three injection modes, suggesting that the fundamental mechanism of vaporization in all three sprays is the same. For the reacting cases, swirling air increases the production of fuel vapor in both time and space compared to the non-swirling air case. The change in vaporization rate shows a trend similar to the non-reacting case, although the rate of change is negative in the region of the reaction zone due to competition between vaporization and consumption. © 1992 Combustion Institute.