Cold air flow velocities were measured in a commercial recovery boiler during shutdown periods, using hot-wire anemometers, modified to indicate direction. Five tests were carried out using different primary and secondary air configurations. The conditions tested included arrangements recommended by others to improve gas flow uniformity, as well as unrealistic extremes to be used in the evaluation of computational fluid dynamic models. The measurements demonstrated the inherent unsteadiness of recovery boiler flows and confirmed that balanced air flows through opposed walls result in a central region of high velocity upward flow. Interlacing of the secondary air significantly reduced the peak velocity and flattened the upward velocity profile at the liquor gun level.