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15.2 Source Sampling 449

Method 1: Sample and velocity transverse for stationary sources
Method 2: Determination of stack gas velocity and volumetric flow rates using
Type S Pitot tube,
Method 3: Gas analysis for the determination of dry molecular weight
Method 4: Characterizing moisture content in stack gases
Method 5: Determination of particulate matter emission from stationary sources
Method 6: Determination of sulfur dioxide emissions from stationary sources
Method 7: Determination of nitrogen oxide emissions from stationary sources
Method 8: Determination of sulfuric acids and sulfur dioxide emissions from
stationary sources

These methods set the foundation for other subsequent methods. The first four
methods are supportive but necessary in that they provide information for other
methods or the calculation of the results. The other four are for the determination of
different air emissions as explicitly indicated by their titles. Method 1 is the first
step for any source testing; it is concerned with assessing the suitability of the
sampling site and determining the sampling points. The principles behind these
Methods will be introduced shortly.
These sampling methods are similar to each other with exchangeable equipment;
this similarity allows a single sampling train to be used by multiple methods by
adding or removing impingers, filters, or other appropriate devices. For example,
Method 5 is typically combined with Methods 2, 3, and 4 in order to determine gas
velocity, molecular weight and moisture content, which are required to calculate a
particulate emission rate. Method 5 and 8 can also be combined by adding addi-
tional impingers and an in-stack filter to the probe on the Method 5 sampling train.
Figure 15.2 shows a schematic diagram of a typical sampling train for Method 5,
which is available online (e.g., http://www.epa.gov for free use). A typical sampling
train starts with a heated probe, or a hollow glass tube that is inserted into the stack
or duct and the last component is a pump drawing gases through the system. Other
pieces of equipment include filters and impingers to capture different air pollutants
of concern. A gas meter measures the flow rate of sampled gas and the stack gas
velocity at the sampling point is measured using a Pitot tube with a manometer
(Sect. 15.1). Finally, the sample exhaust is discharged into the atmosphere through
the orifice, which is used for sample train flow adjustments at the by-pass valve.

15.2.1 Isokinetic Sampling

Isokinetic sampling has to be executed for particulate matter related source tests.
Under isokinetic condition, the gas velocity entering the probe is the same as the
bulk air velocity.