Sampling and Measurement for Respirable Particulates

1. Sampling and Measurement for Respirable Particulates

2. Introduction • Aerosol particle concentration is measured by means of aerosol sampler • Two types of sampling: • Continuous sampling- provides a more statistically consistent result • Batch wise sampling Respirable Particulates

3. Continuous Sampling • Air is drawn through a particulate sampler • Types of particulate sampler: • Filters • Impactors • Direct reading samplers • Flow rate in most cases is less than 2 lit/min Respirable Particulates

4. Filters • Filters are used when sampling for total suspended particles • Air sample is aspirated through one or more openings in the solid casing of the filter holder • The particles are collected on the filter which is subsequently examined Respirable Particulates

5. Filters • Factors affecting selection of filter • Collection efficiency • Pressure Drop • Background contamination • Compatibility with analytical methods • Filters suitable for indoor particles • Cellulose • Fiber • Membrane Respirable Particulates

6. Cascade Impactors • Used to determine total suspended particles and particle size distribution • A multi stage impaction device used to separate airborne particles into size classes on the basis of their aerodynamic diameter • Aerosol is drawn through a series of progressively narrower jets each of which is followed by an impaction surface Respirable Particulates

7. Calibration of test instruments • Two types of test aerosols are generally used: • Monodispersed aerosols – Used to calibrate particle size measuring instruments and to determine the effect of particle size on sampling devices • Polydispersed aerosols- Used in the laboratory to simulate the conditions under which sampler would be used. • Dioctyl phthalate (DOP) is frequently used in testing high efficiency particulate aerosol filters and for calibrating instruments Respirable Particulates

8. Sampling for ETS • No satisfactory technique to measure the particulate matter and chemicals produced from ETS • Method currently used to collect main stream (MS) smoke duplicates the process of puffing a cigarette • Burning end of a cigarette is held under conditions comparable to that of a cigarette being smoked • Most frequently used instrument to generate Side Stream (SS) smoke is the modified Neurath chamber Respirable Particulates

9. Types of Samplers • Traditionally fixed stations (area sampler) has been used • Personal air samplers have been introduced lately • Direct reading particle samplers currently in use are : • Electric aerosol analyzers • Optical particle counters • Integrating nephelometer Respirable Particulates