Granular filtration has been widely used for liquid filtration and hot gas filtration, but less is known for the filtration of airborne particles, especially the ultrafine ones, at the room conditions. A cylindrical packed bed was designed and tested for the filtration of particles in the range of about 10 nm to 15 mu m in diameter at different configurations and kinetic conditions. Three sizes of uniform glass beads (2, 4, and 6 mm in diameter) were tested as the filtration media each at three media thicknesses (H = 2.5, 7.6, and 12.7 cm), and at two airflow rates (50 and 65 liters per minute). The filtration efficiencies were the lowest for particles between 0.1 and 1 mu m in diameter. The particle filtration efficiency decreased with the increase in the granule size and the airflow rate, but a thicker bed corresponded to higher filtration efficiency. The experimental results showed much higher efficiency than existing modeis can predict, therefore, an empirical model using least square method is reported.