Water curtains have been suggested as a way of limiting the spread of ammonia in the event of an accidental release. Several field experiments have already been performed to investigate the interaction between a water curtain and a cloud of ammonia, most recently by Bara and Dusserre (1997, J. Loss Prev. hd, 10(3), 179-183). Those experiments have been modelled numerically, using the computational code Mercure. The calculated velocities and concentrations agree reasonably well with the measurements.