Displacement ventilation in a classroom - influence of contaminant positioning and physical activity.

This study describes how the air quality in a displacement ventilated classroom can beinfluenced by the position of a contaminating person, and by the activity of a person who walksaround in the room. Tracer gas measurements have been performed in a full scale mock-up of aclassroom, with person simulators at the student's desks.The spreading of contaminants from a person seems to be strongly dependent on the positionof the person. The closer the contaminating person sits to the outlet terminal(s), the less ofhishers contaminants are spread in the room. Paradoxically, people sitting furthest away fromthe air supply were found to be provided with the least contaminated air. Physical activity.produced by a walking person, tends to increase the concentration of contaminants emittedfrom people in the room, whereas the air exchange efficiency actually can benefit from it. At alllevels of activity tested in this study the displacement ventilation system provided significantlybetter air quality than a mixing system would.