A displacement ventilation system works better the more uni-directional the air flow through the ventilated room is: from floor to ceiling. Thus, from an air quality point of view, there should be as little vertical mixing of the room air as possible. It is therefore comprehensible that physical activity in the room – like peoples movements – in previous studies has been shown to influence the effectiveness of the ventilation. In this study we have compared results from previous tests, where a cylindrical person simulator was used, to results obtained when using a person simulator of more human-like shape. The main results verify previous findings: if the movements are not very slow, they have a detrimental effect on ventilation effectiveness and on the air quality in the breathing zone of the inhabitants. Some quantitative differences were found between using the simple and the detailed person simulator, although the qualitative results were about the same.