All of the experiments were conducted in a two-dimensional quiescent bed. The cross section was 400 x 15 mm. Glass beads were used as the bed material. The glass bead particle sizes ranged from 69 to 920 mum. The hydrodynamic behavior of gas discharged from a horizontal nozzle was investigated under various operating conditions. The operating parameters included the nozzle diameter, particle size, static bed height and gas velocity through the nozzle. For a single horizontal nozzle, the gas discharge mode under low gas velocity through the nuzzle or high static bed height was void. At high nozzle gas velocity or low static bed height, a horizontal jet was observed. The gas discharge mode changed from void to jet as the Froude number increased.