The air movement in the occupied zone of a room ventilated by displacement ventilation exists as a stratified flow along the floor. This flow can be radial or plane according to the number of wall-mounted diffusers and the room geometry. This paper addresses the situations where plane flow is obtained and a semianalytic expression for the velocity level in the occupied zone is given. It is shown that the flow has a constant velocity level independent of the distance from the diffuser and that the thickness or length scale of the stratified flow has a tendency to be constant everywhere in the flow. The thickness and the velocity are functions of the Archimedes number.