PERSONAL EXPOSURE IN DISPLACEMENT VENTILATED ROOMS

Personal exposure in a displacement ventilated room is examined. The s tratified flow and the considerable concentration gradients necessitat e an improvement of the widely used fully mixing compartmental approac h. The exposure of a seated and a standing person in proportion to the stratification height is examined by means of full-scale measurements . A breathing thermal manikin is used to simulate a person. It is foun d that the flow in the boundary layer around a person is able to a gre at extent to entrain and transport air from below the breathing zone. In the case of non-passive, heated contaminant sources, this entrainme nt improves the indoor air quality. Measurements of exposure due to a passive contaminant source show a significant dependence on the flow f ield as well as on the contaminant source location. Poor system perfor mance is found in the case of a passive contaminant released in the lo wer part of the room close to the occupant. A personal exposure model for displacement ventilated rooms is proposed. The model takes the inf luence of gradients and the human thermal boundary layer into account. Two new quantities describing the interaction between a person and th e ventilation are defined.