It is well known that coarse particles are important because of the characteristics of indoor surface contamination and their deposition to the upper brouchi. Since the raised floor HVAC system (RF system) has been introduced in office buildings, the characterization of redispersion of settled particulates by walking become an important matter of indoor air quality as the outlet is placed on the floor. This paper reports the results mainly obtained from the experiments which determine the amount of redispersive particles, and compare the measured concentration of suspended particles caused by redispersion to the estimated concentration calculated from the settling rate and mixing factor in the space between RF system and conventional ceiling diffuser system (CC system). The main results are shown as follows. (1) The amount of redispersive particles found on the tile carpet was 20 times more than that on the synthetic resin sheet. (2) The vane angle of floor outlet would contribute to the air distribution in indoor environment. With the normal floor outlet, the indoor air distribution was similar to CC system. (3) We can apply the model included settling rate and mixing factor to evaluate the concentration of suspended particles caused by redispersion both into the space with RF system (normal floor outlet) and CC system. The settling rates are 1.0(h^<-1>) for 2 to 5 μm and 2.9(h^<-1>) for larger than 5 μm particles under the condition that mixing factors are 0.84 for RF (normal outlet) and 0.70 for CC system, respectively.
