Abstract
In order to estimate and control the contamination by the airborne particles through the mechanism of settlement it is necessary to analyze the mechnism of falling particles in the atmosphere indoor as well as outdoor. The quantity of settled particles depend upon the concentration, exposure time and terminal velocity which are the function of aerodynamic diameter of the particle, and consequently the size distribution of the settled particles greatly differ from the original ones. In case of outdoors, the quantity of settled particles are obtained by the integral of product of partial distribution and terminal velocity of the particle using particle size distribution. The calculated values were fairly close to those experimentally obtained. In case of indoors, the authors analyzed the relation of quantity of settled particles and the airborne concentration and obtained the general equation which shows that the settled contamination is dependant on the concentration, particle size distribution which determin the terminal velocity, the ceiling height, and the air change rate which is the reciprocal of the time length of particles' stay within the room. Experiments were performed using model chamber of 30 ×30×30 cm in size with known ventilation rate. Theoretical values coincided with the results of experiment very well.
