Bases on the concept of task/ambient ventilation, fresh air can be decoupled from re-circulated air so as to improving ventilation effectiveness in breathing zone. Ceiling mounted high velocity circular jet diffusers, which are regarded as remote personalized ventilation air terminal devices (PV ATDs) without affecting room aesthetic effects, can be utilized to supply fresh air without causing draft rating because tropically acclimatized occupants prefer slightly higher air movement. Under-floor air diffusers are used to supply re-circulated air. Corresponding mixing ventilation system by only utilizing underfloor air diffusers are compared with this task/ambient ventilation system. Numerical simulation using a validated computational fluid dynamics (CFD) model for circular jet diffusers is conducted to investigate the difference between task/ambient ventilation systems and mixing ventilation systems. Location weighted personal exposure effectiveness is utilized as an evaluation index for evaluating indoor air quality (IAQ). Air velocity and temperature are utilized as evaluation indices for evaluating thermal comfort level.