This study investigated effectiveness of negative ionic air purifier in lowering the concentration of particles in a closed test chamber. The performance test was carried out in a closed test chamber under natural decay, as well as with an air mixing mechanism. Compared with natural decay, the air mixing mechanism could reduce particles concentration better (under the flow field condition). However, air change rate effect is limited in super cleanrooms that require suitable approaches to enhance control of particles concentration and to raise the effective cleaning rate of negative ionic air purifier. This study investigated the concentration gradient of particles at various heights and distances from the source of negative ions. Experiment results indicate that performance near the negative ionic purifier was better than in the rest of the cleanroom. In terms of height, the highest removal efficiency was observed at a height of 60 cm from the floor; it decreased substantially with increase in height. The empirical curves fit based for the concentration gradient of NAI generated was developed for estimating the NAI concentration at different heights and distances from the source of negative ionic air cleaner.