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What is Air sampling?

"Air sampling is capturing the contaminant from a known volume of air, measuring the
amount of contaminant captured, and expressing it as a concentration
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 The flow rate of air through the collection medium
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 The amount of contaminant collected
The volume of air is calculated by multiplying the flow rate through the collection medium by
the sample run time
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Flow x Time = Volume of air sampled
The concentration is calculated by dividing the amount of contaminant collected by the
volume of air sampled, and it is expressed either as milligrams per cubic metre (mg/m) or
parts per
million (ppm)
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As the air passes through the sampler, any contaminants present are captured onto a
collection medium (normally a filter paper for solid contaminants and a sorbent for gases)
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The UK Health & Safety Executive publishes guidance on the recommended methods of
monitoring exposure to substances with a WEL: Methods for the Determination of
Hazardous Substances, which can be found on their website www
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qov
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There are
also some internationally adopted (ISo) standards that are used for some contaminants
such as welding
fume
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This means that the sample must be a 'personal' sample,
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taken from within the employee's personal breathing zone (see image below)
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Dust conventions

Dust or 'aerosol' is split into three size ranges as detailed in the diagram to the right, each of
which has different effects on the respiratory system
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Thoracic dust is taken to be solid particles which can be drawn past the larynx
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It is important to note that inhalable dust contains both
thoracic and respirable particles, and in the same way thoracic dust contains
respirable particles
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It is because of this ability to stay in the
body that it is considered to be dangerous; the particles can settle onto the lining of the
lungs and cause respiratory illness such as silicosis or COPD (Chronic Obstructive
Pulmonary Disease)
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The conventions are described in detail in the
European Standard EN481:1993 Workplace atmospheres - Size fraction definitions for
measurement of airborne particles
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Gravimetric analysis is
usually used to measure results (i
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by measuring the weight gain of the filter)
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Filter Sampling Respirable Dust: The I0M* sampler with a special foam plug
placed in the cassette inlet can be used to sample respirable dust
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Filter Sampling Respirable Dust (Alternative Method): The Cyclone Sampler
uses a cyclonic action to separate out the fine respirable dust which is captured on a
filter paper mounted inside a cassette at the top of the sampler
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*Manufactured under license from the Institute ofOccupational Medicine TM 2043339E
Sorbent Sampling: Sorbents are normally contained in a small glass tube with sealed
ends
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The trapped contaminants are released from the sorbent (desorbed), for
laboratory analysis, using solvent washing or heat
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Bag Sampling: Particularly suitable for 'grab' or Short Term Samples (STS), the air is
passed through a sample pump into a special plastic bag
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The bag containing a
relatively large volume of sampled air, is then taken to the laboratory for analysIs
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The pollutant dissolves in the
liquid and is subsequently analysed, usually by colorimetric techniques
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