AIRBORNE PARTICLE SIZE ANALYSIS AND MEASUREMENT TECHNIQUES

摘要

All the mineral particles in a soil are never of same size. The distribution of particle size determines the tenure of the soil whether it is predominantly sandy, loamy or clayed one. A dozen particles are settling through the air in a room. One of them is a perfect sphere of water (smooth surface and density of 1g/cm{sup}3) with a physical diameter of 5 micron. The others are typical of airborne particles in indoor and outdoor atmospheres. One is a fibre, other is a flake and third one is a chain aggregate with 100 tiny particles. One is a small, heavy metallic particle while other is a large piece of expanded plastic foam. All have different color but they all settle down with different Brownian motion. A prototype instrument, based on scattering phenomena, has been developed to measure individual airborne particles according to their size. The goal of the instrument is to provide real-time data indicative of particle characteristics and it is targeted to respond to aerosols from 0.5 to 25 microns diameter. The measurement of fine particles in the size range 0.5 to 1.0 micron, having deep penetration and prone to serious health hazards, will be of more concern.