Sampling Train

Sampling Train
Sample Setup Guide
Sampling Train — Pre-filter and Tube
Sorbent tube sampling is the NIOSH/OSHA-approved method for collecting most hazardous gases and
vapors from the air. Filters are used to sample airborne particulate chemical hazards. Occasionally, it
is necessary to sample simultaneously for gases or vapors and particulates or to eliminate particulates
from the sample. In such cases, a sorbent tube is used with a pre-filter in line. This Sample Setup
Guide demonstrates how to set up a Sampling Train for Pre-filter and Tube Sampling.
In most cases, such sampling is performed in low flow mode. The equipment list and other details of
this guide assume low flow. Check the method in each case to verify recommended flow. If high flow
(> 1000 ml/min) is stipulated, eliminate low flow items from the equipment list and select high flow
equipment as specified in the Sample Setup Guide for Filter and Cyclone Sampling (Publication 1166).
1. An air sampling pump capable of sampling at the
recommended flow rate with the sampling medium
in line, such as:
• SKC Universal Series with a Cat. No. 224-26 Series
Adjustable Low Flow Holder
• SKC AirChek® Series (with Constant Pressure Controller
Cat. No. 224-26-CPC and a 224-26 Series Adjustable
Low Flow Holder)
2. An airflow calibrator
3. The sorbent sample tube specified in the method
4. The SKC filter and cassette blanks specified in the
5. SKC Collar Clip and Cable Ties Cat. No. 225-13-6
6. PTFE tubing
7. Spacer or stainless steel screen
To determine the correct flow rate for the chemical of interest,
refer to the appropriate analytical method. See the operating
instructions for the pump to ensure that it is capable of
sampling at the correct flow rate.
1. Preparing the Filter Cassettes — Figure 1
The filter cassette blank holds the filter securely in place
during sampling. The
cassette consists of an inlet
section, an outlet section,
and possibly a middle ring or
extension cowl. The cassette
with all three sections can
be used with the inlet in
place (closed face) or with
the inlet removed (open
face) depending on the
sampling method. The filter
is assembled as described
below and as shown in
Figure 1.
Air Flow
Required Equipment
Optional Equipment
1. Cassette Shrink Bands Cat. No. 225-25 Series
2. SKC Tube Breaker Cat. No. 222-3-50 (for 6 and 7-mm OD
tubes) or Cat. No. 222-3-51 (for 8 and 10-mm OD tubes)
To load the cassette, place
the appropriate stainless
Figure 1. Filter assembly
steel screen, support pad,
or spacer in the outlet of the
cassette and add the appropriate filter. Insert the extension
cowl or middle ring if required, then close the cassette firmly
with the inlet section. Assemble a second "representative"
cassette for calibrating the flow rate (not for collecting the
sample). Insert plugs into the inlets and outlets of each
cassette until ready to use. Seal both cassettes with shrink
bands (optional).
Publication 1164 Rev 1602
SKC Inc. 724-941-9701
SKC South 434-352-7149
SKC Gulf Coast 281-859-8050
SKC-West 714-992-2780
Sampling Train — Pre-filter and Tube
2. Preparing the Sorbent Tubes
Using a tube breaker, break both ends of a sorbent tube to
provide an opening of at least one-half the internal diameter of
the tube. Cap the ends of the tube until ready to use. Prepare
a second "representative" sorbent tube for calibrating the flow
rate (not for collecting the sample).
Collar Clip and
Cable Tie
3. Setting Up the Calibration Train
If using a Universal Series pump, connect an adjustable
low flow holder to the pump inlet. If using an AirChek Series
pump, connect a Constant Pressure Controller (CPC) plus
adjustable low flow holder to the pump inlet. See the operating
instructions for the CPC for details. Remove the caps from the
representative sorbent tube and insert it into the black rubber
sleeve of the holder. The printed arrow on the sorbent tube
shows the direction of airflow and should be pointed toward
the holder. If there is no arrow printed on the tube, insert the
end of the tube with the smallest sorbent section (backup
section) into the holder.
Remove the plugs from the representative filter cassette.
Using PTFE tubing, connect the cassette outlet to the tube
inlet. With additional tubing, connect the cassette inlet to the
external calibrator. Luer adapters can be used to connect the
filter cassette to the tubing.
Note: Universal Series pumps do not require the CPC.
4. Calibrating the Flow Rate
Ensure pump has run for 5 minutes before calibrating. With
the representative sampling media (loaded filter cassette and
sorbent tube) in line, calibrate the flow rate specified in the
analytical method for the chemical of interest. If using an
adjustable low flow holder, use the flow adjust screw on the
holder to adjust flow rate. Refer to the pump and calibrator
instructions for correct calibration of flow rate. When the
flow rate has been calibrated and verified, remove the filter
cassette and sorbent tube used for calibrating the flow rate
and set these aside. They will be used again for verifying the
flow rate after sampling has been completed. Record the presample flow rate. Remove the external calibrator.
5. Sampling — Figure 2
When ready to start sampling, prepare a sampling train
identical to the one used for calibrating the flow rate, but
without the external calibrator. Insert a new filter cassette
loaded with the appropriate spacer or stainless steel screen
and filter and a new sorbent tube (Figure 2). Attach the
cassette to a worker's clothing near the breathing zone and the
pump to the worker’s belt. The inlet of the cassette should
be facing down. Remove the plug from the cassette inlet (if
applicable). Turn on the pump and note the start time and any
other sampling information.
Low Flow
Pump Inlet
Figure 2. Sampling train using a pre-filter cassette and
a sorbent tube
6. After Sampling
At the end of the sampling period, turn off the pump and note
the ending time. Remove the filter cassette from the worker
and cap the inlet and outlet of the cassette with the plugs
provided. Remove the sorbent tube, seal the ends of the
tube with the caps provided, and record pertinent sampling
Use representative sampling media (filter cassette and tube)
to verify that the flow rate has not changed by more than 5%.
Submit field blanks from the same lot numbers as the
sampling tubes and filters. Field blanks should be subjected to
exactly the same handling as the samples (tubes are opened;
cassettes are loaded with a filter and supports) except that
no air is drawn through them.
Pack the sorbent sample tubes, filter sample cassettes, field
blanks, and all pertinent information securely for shipment to
a laboratory for analysis.
Copyright 1996 - 2016
Notice: This publication is intended for general information only and should not be used as a substitute for reviewing applicable government regulations, equipment operating instructions, or legal standards. The
information contained in this document should not be construed as legal advice or opinion nor as a final authority on legal or regulatory procedures.
Publication 1164 Rev 1602
SKC Inc. 724-941-9701
SKC South 434-352-7149
SKC Gulf Coast 281-859-8050
SKC-West 714-992-2780
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