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Calibration of aerosol instruments.
Chen BT; Fletcher RA; Cheng Y-S
Aerosol measurement: principles, techniques, and applications, third edition. Kulkarni P, Baron PA, Willeke K, eds. Hoboken, NJ: John Wiley and Sons, Inc, 2011 Jan; :449-478
A vast amount of knowledge concerning aerosol properties has been obtained using instruments. These instruments can be categorized as: (1) collection devices such as cascade impactors, virtual impactors, Aitken-type condensation nuclei counters, or filter samplers, which are designed to remove particles from gas streams to obtain samples for analysis; and (2) real-time, direct-reading instruments such as optical particle counters, condensation particle (or nucleus) counters, aerosol electrometers, or photometers. Ideally, instrument response canbe theoretically computed based on equations and procedures described in the previous chapters. Theoretical prediction of instrument response based on ideal conditions may not always be realized. For example, although 50% effective cutoff diameters and collection efficiencies for an impactor stage can be computed, the phenomena of particle bounce, re-entrainment, electrostatic charge effects, and wall losses can modify its performance (Rao and Whitby 1978; Cheng and Yeh 1979). Therefore, experimental calibration is essential. Instruments are usually calibrated and evaluated by the manufacturer or the inventor before being used by others. For an instrument intended to collect an aerosol for analysis, collection efficiency and wall loss are generally determined in the calibration. For a real-time, direct-reading instrument, calibration establishes the relationship between an instrument's response (e.g., electronic signal or channel number) and the value of the property (e.g., particle size, number concentration, or mass concentration) being measured. However, the operating conditions and the parameters used during the original calibration can vary from those under which the eventual user operates. As a result, the original calibration data may not apply, and the user must calibrate the instrument to operate it with confidence. In general, a reliable and accurate calibration requires (1) sufficient knowledge of capabilities and limitations of the instrument, (2) adequate information on the environment where the instrument will be used, (3) appropriate test facilities, (4) proper selection of a desired test aerosol, (5) a thorough investigation of relevant parameters, and (6) a quality assurance program that is followed throughout the test. In the last three decades, developments in aerosol generation and classification, progress in electron microscopy and imaging analysis, and improvement of test facilities have made instrument calibration easier and the results more reproducible. This chapter reviews calibration techniques relevant to aerosol measurement devices, such as sizing instruments, condensation particle counters, and mass monitors. The generation methods for test aerosols and important parameters in instrument calibration are emphasized. Also reviewed are the calibration and use of flow-monitoring devices that play an integral role in aerosol sampling and instrument calibration.
Aerosol-particles; Aerosols; Aerosol-sampling; Airborne-particles; Equipment-design; Equipment-reliability; Filtration; Measurement-equipment; Microscopic-analysis; Nanotechnology; Optical-analysis; Particle-aerodynamics; Particle-counters; Particulate-dust; Particulates; Particulate-sampling-methods; Sampling; Sampling-equipment; Sampling-methods; Standards; Testing-equipment
Kulkarni P; Baron PA; Willeke K
Aerosol measurement: principles, techniques, and applications, third edition
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division