Direct-reading instrumentation for workplace aerosol measurements. A review

A state-of-the-art review of direct-reading instruments capable of near real-time measurement, with particular emphasis on workplace applications, is presented. Considerable advances have been made in recent years owing to the availability of modern transducer technologies and electronic components. Instruments are now available to measure aerosol number concentrations up to 10⁶ particles cm^-3, mass concentration up to 1000 mg m^-3 and size distribution over a size range from 0.003 to > 100 μm. With a wide array of available commercial instruments, it is necessary for practitioners to understand well the operating principles of the instruments and the aerosol system under study. The criteria for selecting an appropriate instrument include the particle size range of interest, the system parameters to be studied and the cost and compactness of the instrument. A flow chart has been prepared to help select a direct-reading instrument for analysing airborne particles. The first step is to decide whether to perform measurements of an integral concentration or a complete size distribution. There are many compact, inexpensive instruments available for integral concentration measurements compared with the more sophisticated, expensive instruments for size distribution measurements. Considerable cost savings can be realized if an integral concentration detector is deemed appropriate for the application. This paper reviews the available integral concentration detectors and the size distribution analysers for workplace aerosol measurements. Some of the exciting recent developments in instrumentation are also described.