Normal and rapid response sprinklers were assessed for their potential in reducing the hazard to life, resulting from fire in department store sales areas, by simulating such fires and adopting a criterion based on the optical density of smoke at 2 m above the floor. Experiments with upholstered lounge furniture fires in a closed rig (30 m x 27 m x 3 m high) suggest that rapid response sprinkler heads in an FOC Ordinary Hazard installation might delay attainment of the hazard criterion by only 15 s in comparison with unsprinklered fires. However, no increased hazard resulted from the use of sprinklers for the circumstances examined there was no transport of smoke by the water spray to below the smoke layer which appeared to be of almost uniform depth over most of the ceiling area with little increase in depth near the walls. Further experimental work is proposed to examine the effects of reduced sprinkler spacing and other water densities.