The purpose of this work was to quantify the deposition constant of size classified particles under three different air change rates. The experiments were conducted in a small-scale acrylic chamber at Syracuse University. The particle size range was from 0.723 to 5.048 urn with 28 size bins. The air change rates were about 6, 11 and 13 1/hr. TSI large particle aerosol generator 8108 was used to generate potassium chloride as test particles, and the TSI aerodynamic particle sizer (APS3321) was used to measure the particle concentrations. Particle deposition constants were determined by regression fitting of the measured time and size-resolved particle number concentrations. Air change rates were measured by TSI mass flow meter 40241. The calculated particle deposition constants were dependent on the sizes. The small particles had low deposition constants because of the weak Brownian motion and gravitational settling. The large particles were mainly affected by the gravity. However, the results showed the air change rates did not affect the deposition constant significantly for the particle size range studied. The experiment results had a good agreement with the empirical model prediction. The study also proposed a new dimensionless deposition constant k+ to compare different studies for particle deposition indoors. By using k+, the current small-scale chamber test agrees very well with previous full-scale chamber studies even under different test conditions (test particle, size range, surface material, air change rate, surface to volume ratio and test chamber).