In the indoor air quality (IAQ) assessment of ventilated enclosures it is useful to know therelative influence of key boundary conditions on the personal exposure and ventilationeffectiveness, for instance as a source of information on where to allocate the greatest effortin the design phase. CFD is used to predict ventilation effectiveness and personal exposure tocontaminant sources in a displacement ventilated room subject to variation of several keyboundary conditions. The influence is studied regarding the relative influence of room height,wall heat flux, air change rate and Archimedes number for two different contaminant sourcetypes. The results show how IAQ may be significantly influenced by changes of the keyparameters although with differences in the relative influence. Tendency information providesrough guidance on parameter sensitivity to changes.