1104 STACK SAMPLING
0.3 percentage points when used for above purposes. When
only the molecular weight determination is desired, the anal-
ysis is repeated until the dry molecular weights from any
three analyses differ by less than 0.32 g/g-mole (lb/lb-mole).
The Fyrite analyzer can be used only for determination of
molecular weight.
Sampling is done in one of three methods: grab, inte-
grated, or multi-point integrated. Grab samples are used
when the source is spacially uniform and concentration as a
function of time is required, or the source is considered uni-
form over time. Integrated samples are the most commonly
used. A leak-free 30 liter plastic bag is filled using a pump
and flow meter to insure that the sample is representative
of the same period of time as the emission test. Bags must
be analyzed within 8 hours for determination of molecular
weight, or 4 hours when samples were collected for emis-
sion rate correction. For a multi-point integrated sample, the
stack is traversed as described in Method 1. Samples are uni-
formly collected in suitable sampling bags.
Leak-checks of the analyzer and bags are required. The
leak-check should also insure that the valve does not leak in
the open position. To assure the data quality when both O 2
and CO 2 are measured, a fuel factor, F 0 , should be calculated
using the equation:F20.9 %O(^0) %CO
2
2
The value of F 0 should be compared with the values given
in the Test Method for the fuel used. If F 0 is not within the
specified range, the source of error must be investigated.
The EPA Test Method 3 write-up contains detailed
instructions, along with a list of references. It should be
read in detail before the Method is attempted. As with all of
these methods, testing should be performed only by trained
and experienced personnel using equipment and materials
designed for this purpose.
Test Method 3C
Test Method 3C is a gas chromatographic method used to
measure CO 2 , CH 4 , N 2 and O 2 from landfill gases.
Test Method 4
Test Method 4 is used to determine moisture content in stack
gases. In this method a sample is extracted at a constant rate
from the stack; the moisture is removed and determined
either gravimetrically or volumetrically. Often this measure-
ment is made as part of particulate emission measurements.
When saturated conditions are present in the stack gases,
(i.e. water droplets are present), the test method may yield
questionable results. Moisture content for saturated stack
gases should be based on stack temperature measurements
and either phschrometric charts or vapor pressure tables.
Molecular weight determinations and velocity calculations
should be based on the lower of the two water concentration
determinations.
The procedure described next for Method 5 is appropriate
for Method 4. If particulate measurements are not required,
the method can be simplified as follows:
- The filter required in Method 5 can be replaced
with a glass wool plug. - The probe need be heated only enough to prevent
condensation. - The sampling rate does not have to be isokinetic,
instead the source can be sampled at a constant
rate within 10%.
The EPA Test Method 4 write-up contains detailed instruc-
tions, along with a list of references. It should be read in
detail before the Method is attempted. As with all of these
methods, testing should be performed only by trained and
experienced personnel using equipment and materials
designed for this purpose. A table for determination of vapor
pressure of water at saturation is located in section 3.3.6
page 7 of the Quality Assurance Handbook of Air Pollution
Measuring Systems: Volume III.
Test Method 5
Test Method 5 is used to measure particulate emissions
from stationary sources. Stack gases containing particu-
late matter are drawn isokinetically through a glass fiber
filter. The volume of gas after removal of all water is mea-
sured with a dry gas meter. The particulates are measured
gravimetrically.
The equipment used in Method 5 forms the basis for
many other emission measurements, therefore, the compo-
nents of the Method 5 Train, Figure 6, will be described in
some detail.
Probe Nozzle
The probe nozzles are usually stainless steel tubing in the
shape of a Shepherd’s Crook with a sharp tapered opening.
Nozzles are available in a variety of sizes from 1/8” to 3/4”
in diameter. They are calibrated by measuring the diameter
in three different directions. The difference between the
high and low value must be less than 0.004”. The nozzle tips
should be inspected before each use to ensure that the nozzle
has not been damaged. During the sample recovery phase,
all external particulate matter is wiped off and the opening
capped with aluminum foil. When the probe has cooled suf-
ficiently, the nozzle is removed. The nozzle is then cleaned
by rinsing with reagent grade acetone and brushing with
a Nylon bristle brush until further rinses with acetone are
free of particulates. The acetone is saved in a bottle labeled
Container 2 for later analysis.
Probe
Probe liners are usually constructed of borosilicate glass, or,
if stack temperatures are expected to exceed 480ºC, quartz.
Metal liners can be used subject to EPA approval. The
probe liner is wrapped wit heater tape to maintain tempera-
tures adequate to prevent condensation. The temperature of
C019_003_r03.indd 1104C019_003_r03.indd 1104 11/18/2005 11:07:15 AM11/18/2005 11:07:15 AM