Impingement of dust-laden gas on a confined liquid surface is analysed theoretically by assuming negligible viscous effect of the gas and no interaction of dust movement with the gas flow field. The analysis indicates that for a specific dust size there exists a certain nozzle size below which die dust is removed completely. The dust-removal efficiency eta depends on the impaction number N(I), die vertical gas velocity at the center of the nozzle exit lambda, and the nozzle half-width r according to the equation lambdaeta + [2/(pi - 2)](1 -lambda)(sin-1 eta - eta) = N(I)[(1/r) - eta].