ASTM F50, “Standard Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using Instruments Capable of Detecting Single Sub-Micrometre and Larger Particles,” has just been revised and is now available from Document Center Inc. in either paper or pdf format. The 6-page standard describes a procedure for collecting near real-time data on airborne particle concentration and size distribution in clean areas as indicated by single particle counting techniques. It replaces the ASTM F50-07 from 2007 which is now obsolete.
The processing requirements of many products manufactured in a clean room involves environmental cleanliness levels so low that a single particle counter with capability for detecting very small particles is required to characterize clean room air.
Real-time information on concentration of airborne particles in size ranges from less than 0.1 μm to 5 μm and greater can be obtained only with an SPC (single particle counting device). Definition of particles larger than approximately 0.05 μm may be carried out with direct measurement of light scattering from individual particles. Other techniques may be required for smaller particles, such as preliminary growth by condensation before particle measurement. Implementation of some government and industry specifications requires acquisition of particle size and concentration data using an SPC.
In applying ASTM F50-12, the fundamental assumption is made that the particles in the sample passing through the SPC are representative of the particles in the entire dust-controlled area being analyzed. Care is required that good sampling procedures are used and that no artifacts are produced at any point in the sample handling and analysis process; these precautions are necessary both in verification and in operation of the SPC.
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Tags: ASTM F50, ASTM F50-12, Standard Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using Instruments Capable of Detecting Single Sub-Micrometre and Larger Particles