SAMPLE AND VELOCITY TRAVERSES

FOR STATIONARY SOURCES

(Method 1)

Scope and Application

 Measured parameters:

o The purpose of the method is to provide guidance for the selection of sampling
ports and traverse points at which sampling for air pollutants will be performed.
o Two procedures are presented: a simplified procedure, and an alternative
procedure.
o The magnitude of cyclonic flow of effluent gas in a stack or duct is the only
parameter quantitatively measured in the simplified procedure.

 Applicability:

o This method is applicable to gas streams flowing in ducts, stacks and flues.
o This method cannot be used when:

 The flow is cyclonic or swirling

 Stack is smaller than 0.3 meter in diameter, or 0.071 m 2 in cross-sectional
area.

o The simplified procedure cannot be used when the measurement site is less than
two stack or duct diameters downstream or less than a half diameter upstream
from a flow disturbance.

Summary of Method

This method is designed to aid in the representative measurement of pollutant emissions

and/or total volumetric flow rate from a stationary source. A measurement site where the effluent
stream is flowing in a known direction is selected, and the cross-section of the stack is divided
into a number of equal areas. Traverse points are then located within each of these equal areas.

Selection of Measurement Site

 Sampling and/or velocity measurements are performed at a site located at least eight
stack or duct diameters downstream and two diameters upstream from any flow
disturbance such as bend, expansion or contraction in the stack, or from a visible flame.
 If necessary, an alternative location may be selected, at a position at least two stack or
duct diameters downstream and a half diameter upstream from any flow disturbance.
Determining the Number of Traverse Points

 Particulate Traverses

o When the eight- and two-diameter criterion can be met, the minimum number of
traverse points shall be:

 Twelve (12), for circular or rectangular stacks with diameter (or equivalent
diameters) greater than 0.61 m
 Eight (8), for circular stacks with diameters between 0.30 and 0.61 m
 Nine (9), for rectangular stacks with equivalent diameters between 0.30
and 0.61 m

Location of Traverse Points

 For stacks having diameters greater than 0.61 m

o No traverse points shall be within 2.5 cm of the stack walls

 When any of the traverse points fall within 2.5 cm of the stack walls,
relocate them away from the stack walls to a distance of 2.5 cm or a
distance equal to the nozzle inside diameter, whichever is larger. These
relocated traverse points (on each end of a diameter) shall be the
“adjusted” traverse points.

 For stacks diameters equal to or less than 0.61 m

o No traverse points shall be located within 1.3 cm of the stack walls

 Any “adjusted” points should be relocated away from the stack walls to a
distance of 1.3 cm or a distance equal to the nozzle inside diameter,
whichever is larger.
 DETERMINATION OF STACK GAS VELOCITY
AND VOLUMETRIC FLOWRATE
(Method 2)

This method is applicable for the determination of the average velocity and the
volumetric flow rate of a gas stream using an S type pitot tube. This method is not applicable at
measurement sites that fail to meet the criteria of Method 1. Also, the method cannot be used for
direct measurement in cyclonic or swirling gas streams.

Type S Pitot tube

 Made of metal tubing with an external diameter between 0.48 and 0.95 cm.
 There shall be an equal distance from the base of each leg of the pitot to its face-opening
plane.
 The face openings shall be aligned; however slight misalignments are permissible.
 The pitot shall have a known coefficient. If a baseline coefficient value of 0.84 is
assigned to the pitot tube and upon inspection does not meet the criteria, that pitot tube
will not be used.

Procedure

 A pretest leak check of the pitot tube and manometer will be conducted.
 The manometer will be leveled and zeroed prior to use as well as periodically checked
during the test.
 The velocity head and temperature will be measured at each traverse point specified by
Method 1.
 The static pressure in the stack will be measured during the test as well as the
atmospheric pressure.
 GAS ANALYSIS FOR THE DETERMINATION OF
DRY MOLECULAR WEIGHT
(Method 3)

Applicability and Principle

This method is applicable for the determination of CO2 and O2 concentrations and dry
molecular weight of a sample from an effluent gas stream of a fossil-fuel combustion process
and other process. The sample is taken in a flexible bag and analyzed in an orsat analyzer.

A gas sample is extracted from a stack by either a single point integrated or multi-point
integrated sampling. The gas sample is analyzed for percent CO2, O2, and if necessary CO.

Apparatus

 Pump

o A leak free diaphragm-type pump, or its equivalent, to transport the sample to the
flexible bag.

 Rate Meter

o A rotameter, or equivalent, capable of measuring flow rate to within 2 percent of

the selected flow rate will be used.
o A flow rate of 500 to 1000 cc/min will be used unless another rate is required.

 Flexible Bag

o Any leak free plastic (Tedlar, Teflon, Mylar, etc.) bag or equivalent having a
capacity consistent with the selected flow rate and sample time

 Pressure Gauge

o A water filled U-tube manometer, or equivalent, of about 30 cm for the bag leak
check.

 Vacuum Gauge

o A mercury manometer, or equivalent, of at least 760 mm Hg, for sampling train

check.
Procedure

 Single Point Integrated

o The sampling point will be at the centroid of the cross section of the duct.
o The bag will be leak checked.
o The train will be leak checked.
o The sampling system will be purged prior to connecting the sample bag.
o The sample will be taken at a constant rate simultaneous with, and for the same
total length of time as, each pollutant emission rate determination.
o At least 30 L of sample will be taken.

Emission Measurement Test Procedure

o Within 8 hours of collection, the sample will be analyzed for percent CO2 and percent O2
using an orsat analyzer.
o The orsat analyzer will be leak checked prior to any sample analysis.
o The analysis and calculations for each sample will be repeated until any three analysis
differ from their mean by no more than 0.3 g/gmol.
 DETERMINATION OF MOISTURE CONTENT
IN STACK GASES
(Method 4)

Applicability and Principle

A gas sample is extracted either at a constant rate or utilizing an isokinetic sampling

train; moisture is removed from the sample stream and determined either volumetrically or
gravimetrically.

Apparatus

 Probe

o A stainless steel or glass tubing, sufficiently heated to prevent water

condensation, and is equipped with either an in-stack filter (i.e. glass wool plug)
or heated out of stack filter.

 Condenser

o The condenser will consist of four impingers connected in series with ground
glass, leak-free fittings or any similar non-contaminating fittings.
o The first, third and fourth impingers will be of the Greenburg-Smith design,
modified by replacing the tip with a 1.3 cm ID glass tube extending to about 1.3
cm from the bottom of the flask.
o The second impinger will be of the Greenburg-Smith design with the standard tip.
o The first two impingers will contain known volumes of water, the third will be
empty, and the fourth will contain a known weight of 6 to 16 mesh indicating type
silica gel, or equivalent desiccant.

 Cooling System

o An ice bath container and crushed ice, or equivalent, are used to aid in condensing
moisture.

 Metering System

o This system will include a vacuum gauge, leak-free pump, thermometers capable
of measuring temperature to within 3°C and a dry gas meter capable of measuring
volume to within 2 percent.
  Barometer

o Mercury, aneroid or other barometer capable of measuring atmospheric pressure

to within 2.5 mmHg.

 Graduated Cylinder and/or Balance

o These items are used to measure the condensed water in the impingers and silica
gel to within 1 mL or 0.5 g.
o Graduated cylinders will have subdivisions no greater than 2 mL.
o The balance will be capable of weighing to the nearest 0.5 g or less.

Procedure

 A minimum total gas volume of 0.60 scm will be collected, at a rate no greater than 0.021
m3/min.
 The moisture determination will be conducted simultaneous with, and for the same total
length of time as, the pollutant emission rate run.
 The probe and filter (if applicable) will be heated to about 120 °C, to prevent water
condensation ahead of the condenser.
 After the train is heated and the impingers iced down, a leak check will be performed
with an acceptable rate of 4 percent the average sampling rate or 0.02 cfm, whichever is
less.
 During the run, the sampling rate maintained within 10 percent of constant rate.
 The dry gas meter volume will be recorded at the beginning and end of each sampling
time increment and whenever sampling is halted.
 More ice will be added, if necessary, to maintain a temperature of less than 20°C at the
silica gel outlet.
 When the run is completed, a post leak check is performed, with the same acceptance
criteria as for the pre-test leak check.
 The volume and weight of condensed moisture is measured to the nearest mL and 0.5 g,
respectively.

 In gas streams that contain water droplets, this method may produce a positive bias.
 If this is suspected for this source, either a wet bulb dry bulb and psychometric chart
(correcting for stack pressure) or saturation and vapor pressure table determination will
be conducted simultaneously with the moisture sample train.
 DETERMINATION OF PARTICULATE MATTER EMISSIONS
FROM STATIONARY SOURCES
(Method 5)

Summary of Method

Particulate matter is withdrawn isokinetically from the source and collected on a glass
fiber filter maintained at a temperature of 120 ± 14°C or such other temperature as specified by
an applicable subpart of the standards or approved by the Administrator for a particular
application. The PM mass, which includes any material that condenses at or above the filtration
temperature, is determined gravimetrically after the removal of uncombined water.

Sample Collection

 Sampling Train
Pretest Preparation

o Place 200 to 300 g of silica gel in each of several air-tight containers.

o Weigh each container, including silica gel, to the nearest 0.5 g, and record its weight.
o As an alternative, the silica gel need not be pre-weighed, but may be weighed directly in
its impinger or sampling holder just prior to train assembly.

o Check the filters visually against light for irregularities, flaws, or pinhole leaks.
o Label filters of the proper diameter on the back side near the edge using numbering
machine ink.
o As an alternative, label the shipping containers (glass, polystyrene or polyethylene petri
dishes), and keep each filter in its identified container at all times except during sampling.

o Desiccate the filters at 20 ± 5.6°C and ambient pressure for at least 24 hours.
o Weigh each filter at intervals of at least 6 hours to a constant weight.
o Record results to the nearest 0.1 mg.
o During each weighing, the period for which the filter is exposed to the laboratory
atmosphere shall be less than 2 minutes.
o Alternatively, the filters may be oven dried at 105°C for 2 to 3 hours, desiccated for 2
hours, and weighed.

Preliminary Determination

o Select the sampling site and the minimum number of sampling points
 o Determine the stack pressure, temperature and the range of velocity heads; it is
recommended that a leak check of the pitot lines be performed.
o Determine the moisture content for the purpose of making isokinetic sampling rate
settings.
o Determine the stack dry gas molecular weight

o Select a nozzle size based on the range of velocity heads, such that it is not necessary to
change the nozzle size in order to maintain isokinetic sampling rates.
o During the run, do not change the nozzle size.
o Ensure that the proper differential pressure gauge is chosen for the range of velocity
heads encountered.

o Select a suitable probe liner and probe length such that all traverse points can be sampled.
o For large stacks, consider sampling from opposite sides of the stack to reduce the
required probe length.

o Select a total sampling time greater than or equal to the minimum total sampling time
specified in the test procedures for the specific industry such that

 Sampling time per point is not less than 2 minutes (or some greater time
interval as specified by the Administrator)
 Sample volume taken (corrected to standard conditions) will exceed the
required minimum total gas sample volume.

o The sampling time at each point shall be the same. It is recommended that the number of
minutes sampled at each point be an integer or an integer plus one-half minute, in order
to avoid timekeeping errors.

o In some circumstances it may be necessary to sample for shorter times at the traverse
points and to obtain smaller gas sample volumes. In these cases, the Administrator’s
approval must first be obtained.

Preparation of Sampling Train

 During preparation and assembly of the sampling train, keep all openings where
contamination can occur covered until just prior to assembly or until assembly is about to
begin.
 Place 100 mL of water in each of the first two impingers, leave the third impinger empty,
and transfer approximately 200 to 300 g of pre-weighed silica gel from its container to
the fourth impinger.
 More silica may be used, but care should be taken to ensure that it is not entrained and
carried out from the impinger during sampling.
 Place the container in a clean place for later use in the sample recovery.
 Alternatively, the weight of the of the silica gel plus impinger may be determined to the
nearest 0.5 g and recorded.
  Using a tweezer or clean disposable surgical gloves, place a labeled (identified) and
weighed filter in the filter holder.
 Be sure that the filter is properly centered, and the gasket properly placed to prevent the
sample gas stream from circumventing the filter.
 Check the filter for tears after assembly is completed.

 When the glass probe liners are used, install the selected nozzle using a Viton A O-ring
when stack temperatures are less than 260°C or a heat-resistant string gasket when
temperatures are higher.
 Other connecting systems using either 316 stainless steel or Teflon ferrules may be used.
 When metal liners are used, install the nozzle as discussed above or by a leak-free direct
mechanical connection.
 Mark the probe with heat resistant tape or by some other method to denote the proper
distance into the stack or duct for each sampling point.

 Set up the train ensuring that the connections are leak tight.
 A glass cyclone may be used between the probe and filter holder when the total
particulate catch is expected to exceed 100 mg or when water droplets are present in the
stack gas.

 Place crushed ice around the impingers

Leak check procedure

 That portion of the sampling train from the pump to the orifice meter should be leak-
checked prior to initial use and after each shipment.
 Leakage after the pump will result in less volume being recorded than is actually
sampled.

 Close the main valve on the meter box.

 Insert a one-hole rubber stopper with rubber tubing attached into the orifice exhaust pipe.
 Disconnect and vent the low side of the orifice manometer.
 Close off the low side orifice tap.
 Pressurize the system to 13 to 18 cm water column by blowing into the rubber tubing
 Pinch off the tubing, and observe the manometer for one minute.
 A loss of pressure on the manometer indicates a leak in the meter box; leaks, if present,
must be corrected.

 A pretest leak check of the sampling train is recommended, but not required.
 If the pretest leak check is conducted, the following procedure should be used.
 After the sampling train has been assembled, turn on and set the filter and probe heating
systems to the desired operating temperatures.
 Allow time for the temperatures to stabilize.
 If a Viton A O-ring or other leak-free connection is used in assembling the probe nozzle
to the probe liner, leak-check the train at the sampling site by plugging the nozzle and
pulling a 380 mm (15 in.) Hg vacuum.

 If a heat-resistant string is used, do not connect the probe to the train during the leak
check.
 Instead, leak-check the train by first plugging the inlet to the filter holder (cyclone, if
applicable) and pulling a 380 mm (15 in.) Hg vacuum.
 Then connect the probe to the train, and leak-check at approximately 25 mm (1 in.) Hg
vacuum; alternatively, the probe may be leak-checked with the rest of the sampling train,
in one step, at 380 mm (15 in.) Hg vacuum.
 Leakage rates in excess of 4 percent of the average sampling rate or 0.00057 m3 /min
(0.020 cfm), whichever is less, are unacceptable.

 Start the pump with the bypass valve fully open and the coarse adjust valve completely
closed.
 Partially open the coarse adjust valve, and slowly close the bypass valve until the desired
vacuum is reached.
 Do not reverse the direction of the bypass valve, as this will cause water to back up into
the filter holder.
 If the desired vacuum is exceeded, either leak-check at this higher vacuum, or end the
leak check and start over.

 When the leak check is completed, first slowly remove the plug from the inlet to the
probe, filter holder, or cyclone (if applicable), and immediately turn off the vacuum
pump.
 This prevents the water in the impingers from being forced backward into the filter holder
and the silica gel from being entrained backward into the third impinger.

 Leak Checks During Sample Run.

 If, during the sampling run, a component (e.g., filter assembly or impinger) change
becomes necessary, a leak check shall be conducted immediately before the change is
made.
 If the leakage rate is found to be no greater than 0.00057 m3 /min (0.020 cfm) or 4
percent of the average sampling rate (whichever is less), the results are acceptable, and no
correction will need to be applied to the total volume of dry gas metered; if, however, a
higher leakage rate is obtained, either record the leakage rate and plan to correct the
sample volume, or void the sample run.

 Post-Test Leak Check.

 A leak check of the sampling train is mandatory at the conclusion of each sampling run.
  If the leakage rate is found to be no greater than 0.00057 m3 min (0.020 cfm) or 4 percent
of the average sampling rate (whichever is less), the results are acceptable, and no
correction need be applied to the total volume of dry gas metered.
 If, however, a higher leakage rate is obtained, either record the leakage rate and correct
the sample volume or void the sampling run.

Sampling Train Operation

 During the sampling run, maintain an isokinetic sampling rate (within 10 percent of true
isokinetic unless otherwise specified by the Administrator) and a sample gas temperature
through the filter of 120 ±14 °C (248 ±25 °F) or such other temperature as specified by
an applicable subpart of the standards or approved by the Administrator.

 For each run, record the data required on a data sheet.

 Record the DGM readings at the beginning and end of each sampling time increment,
when changes in flow rates are made, before and after each leak check, and when
sampling is halted.
 Take other readings at least once at each sample point during each time increment and
additional readings when significant changes (20 percent variation in velocity head
readings) necessitate additional adjustments in flow rate.
 Level and zero the manometer. Because the manometer level and zero may drift due to
vibrations and temperature changes, make periodic checks during the traverse.
 Clean the portholes prior to the test run to minimize the chance of collecting deposited
material.
 To begin sampling, verify that the filter and probe heating systems are up to temperature,
remove the nozzle cap, verify that the pitot tube and probe are properly positioned.
 Position the nozzle at the first traverse point with the tip pointing directly into the gas
stream.
 Immediately start the pump and adjust the flow to isokinetic conditions.

 When the stack is under significant negative pressure (i.e., height of impinger stem), take
care to close the coarse adjust valve before inserting the probe into the stack to prevent
water from backing into the filter holder. If necessary, the pump may be turned on with
the coarse adjust valve closed.

 When the probe is in position, block off the openings around the probe and porthole to
prevent unrepresentative dilution of the gas stream.

 Traverse the stack cross-section, being careful not to bump the probe nozzle into the
stack walls when sampling near the walls or when removing or inserting the probe
through the portholes; this minimizes the chance of extracting deposited material.

 During the test run, make periodic adjustments to keep the temperature around the filter
holder at the proper level to maintain the sample gas temperature exiting the filter; add
 more ice and, if necessary, salt to maintain a temperature of less than 20 °C (68 °F) at the
condenser/silica gel outlet. Also, periodically check the level and zero of the manometer.

 If the pressure drop across the filter becomes too high, making isokinetic sampling
difficult to maintain, the filter may be replaced in the midst of the sample run.
 It is recommended that another complete filter assembly be used rather than attempting to
change the filter itself.
 Before a new filter assembly is installed, conduct a leak check.
 The total PM weight shall include the summation of the filter assembly catches.

 A single train shall be used for the entire sample run, except in cases where simultaneous
sampling is required in two or more separate ducts or at two or more different locations
within the same duct, or in cases where equipment failure necessitates a change of trains.

 At the end of the sample run, close the coarse adjust valve, remove the probe and nozzle
from the stack, turn off the pump, record the final DGM meter reading, and conduct a
post-test leak check.

Calculation of Percent Isokinetic

Calculate percent isokinetic to determine whether the run was valid or another test run
should be made. If there was difficulty in maintaining isokinetic rates because of source
conditions, consult with the Administrator for possible variance on the isokinetic rates.

Sample Recovery

 Proper cleanup procedure begins as soon as the probe is removed from the stack at the
end of the sampling period.
 Allow the probe to cool.

 When the probe can be safely handled, wipe off all external PM near the tip of the probe
nozzle, and place a cap over it to prevent losing or gaining PM.
 Do not cap off the probe tip tightly while the sampling train is cooling down. This would
create a vacuum in the filter holder, thereby drawing water from the impingers into the
filter holder.

 Before moving the sample train to the cleanup site, remove the probe from the sample
train and cap the open outlet of the probe. Be careful not to lose any condensate that
might be present. Cap the filter inlet where the probe was fastened.
 Remove the umbilical cord from the last impinger and cap the impinger. If a flexible line is used
between the first impinger or condenser and the filter holder, disconnect the line at the filter
holder, and let any condensed water or liquid drain into the impingers or condenser.
 Cap off the filter holder outlet and impinger inlet. Either ground-glass stoppers, plastic caps, or
serum caps may be used to close these openings.

 Transfer the probe and filter-impinger assembly to the cleanup area. This area should be clean
and protected from the wind so that the chances of contaminating or losing the sample will be
minimized.

 Save a portion of the acetone used for cleanup as a blank.

 From each storage container of acetone used for cleanup, save 200 ml and place in a glass
sample container labeled “acetone blank.”
 To minimize any particulate contamination, rinse the wash bottle prior to filling from the tested
container.

 Inspect the train prior to and during disassembly and note any abnormal conditions.

Container 1

 Carefully remove the filter from the filter holder and place it in its identified petri
dish container.
 Use a pair of tweezers and/or clean disposable surgical gloves to handle the filter.
 If it is necessary to fold the filter, do so such that the PM cake is inside the fold.
 Using a dry Nylon bristle brush and/or a sharp-edged blade, carefully transfer to
the petri dish any PM and/or filter fibers that adhere to the filter holder gasket.
 Seal the container.

Container 2

 Taking care to see that dust on the outside of the probe or other exterior surfaces does
not get into the sample, quantitatively recover PM or any condensate from the probe
nozzle, probe fitting, probe liner, and front half of the filter holder by washing these
components with acetone and placing the wash in a glass container.
 Deionized distilled water may be used instead of acetone when approved by the
Administrator and shall be used when specified by the Administrator.
 Perform the acetone rinse as follows:

o Carefully remove the probe nozzle.

 o Clean the inside surface by rinsing with acetone from a wash bottle and
brushing with a Nylon bristle brush.
o Brush until the acetone rinse shows no visible particles, after which make
a final rinse of the inside surface with acetone.
o Brush and rinse the inside parts of the fitting with acetone in a similar way
until no visible particles remain.
o Rinse the probe liner with acetone by tilting and rotating the probe while
squirting acetone into its upper end so that all inside surfaces will be
wetted with acetone.
o Let the acetone drain from the lower end into the sample container.
o A funnel (glass or polyethylene) may be used to aid in transferring liquid
washes to the container.
o Follow the acetone rinse with a probe brush.
o Hold the probe in an inclined position, squirt acetone into the upper end as
the probe brush is being pushed with a twisting action through the probe;
hold a sample container underneath the lower end of the probe, and catch
any acetone and particulate matter that is brushed from the probe.
o Run the brush through the probe three times or more until no visible PM is
carried out with the acetone or until none remains in the probe liner on
visual inspection.
o With stainless steel or other metal probes, run the brush through in the
above prescribed manner at least six times since metal probes have small
crevices in which particulate matter can be entrapped.
o Rinse the brush with acetone, and quantitatively collect these washings in
the sample container.
o After the brushing, make a final acetone rinse of the probe.
o Clean the inside of the front half of the filter holder by rubbing the
surfaces with a Nylon bristle brush and rinsing with acetone.
o Rinse each surface three times or more if needed to remove visible
particulate.
o Make a final rinse of the brush and filter holder.
o Carefully rinse out the glass cyclone, also (if applicable).
o After all acetone washings and particulate matter have been collected in
the sample container, tighten the lid on the sample container so that
acetone will not leak out when it is shipped to the laboratory.
o Mark the height of the fluid level to allow determination of whether
leakage occurred during transport.
o Label the container to clearly identify its contents.

Container 3

 Note the color of the indicating silica gel to determine whether it has been
completely spent and make a notation of its condition.
 Transfer the silica gel from the fourth impinger to its original container, and seal.
  A funnel may make it easier to pour the silica gel without spilling.
 A rubber policeman may be used as an aid in removing the silica gel from the
impinger.
 It is not necessary to remove the small amount of dust particles that may adhere to
the impinger wall and are difficult to remove.
 Since the gain in weight is to be used for moisture calculations, do not use any
water or other liquids to transfer the silica gel.

Sample Transport

Whenever possible, containers should be shipped in such a way that they remain upright
at all times.