Page 213 - Fundamentals of Air Pollution

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Ambient Air Sampling

I. ELEMENTS OF A SAMPLING SYSTEM

The principal requirement of a sampling system is to obtain a sample
that is representative of the atmosphere at a particular place and time and
that can be evaluated as a mass or volume concentration. Remote monitor-
ing techniques are discussed in Chapter 15. The sampling system should not
alter the chemical or physical characteristics of the sample in an undesirable
manner. The major components of most sampling systems are an inlet
manifold, an air mover, a collection medium, and a flow measurement
device.
The inlet manifold transports material from the ambient atmosphere
to the collection medium or analytical device, preferably in an unaltered
condition. The inlet opening may be designed for a specific purpose. All
inlets for ambient sampling must be rainproof. Inlet manifolds are made
out of glass, Teflon, stainless steel, or other inert materials and permit the
remaining components of the system to be located at a distance from the
sample manifold inlet. The air mover provides the force to create a vacuum
or lower pressure at the end of the sampling system. In most instances,
air movers are pumps. The collection medium for a sampling system may
be a liquid or solid sorbent for dissolving gases, a filter surface for collecting
particles, or a chamber to contain an aliquot of air for analysis. The flow

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