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Sampling and Measurement for
Respirable Particulates
Respirable Particulates
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
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
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
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
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
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
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
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