The rising stream around a human body attributable to metabolic heat can carry contaminants from the floor level to the human breathing system. Thus, the quality of the breathing air greatly depends on the concentration distribution in the lower part of the room and the characteristics of the local air motion around the body. In this paper, a modeled human body (computational thermal manikin) is placed in a room that is air-conditioned with a displacement ventilation system. Flow and temperature fields around the manikin are analyzed by computational fluid dynamics (CFD) using a low-Reynolds-number type k-e model. Based on the predicted flow field, the age of supply air and the residual lifetime of air in the room are also numerically calculated by CFD. Three cases of prediction of the concentration distribution are carried out with different locations of contaminant generation. The quality of the breathing air is assessed using the newly defined index, indicating the effective entrainment ratio of the lower region air to the breathing air. Results of the CFD analysis agree well with previous experimental data.

Units: SI