A Guide to Whole Air Canister Sampling

A Guide to Whole Air Canister Sampling

Equipment Needed and Practical Techniques

for Collecting Air Samples

TECHNICAL GUIDE

Inside:

Introduction  . . . . . . . . . . . . . . . . . . . . .2

Equipment Used  . . . . . . . . . . . . . . . . .2

Preparing the Sampling Train  . . . . .6

Preparing the Canister  . . . . . . . . . . .7

Field Sampling  . . . . . . . . . . . . . . . . . . . . .7

Analysis of Collected Samples  . . . .9

Cleaning the Sampling Train  . . . .10

Cleaning the Canister  . . . . . . . . . . .11

Certifying the Canister  . . . . . . . . . .13

Conclusion  . . . . . . . . . . . . . . . . . . . . .14

Air Sampling Products  . . . . . . . . . .15

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I. Introduction
Ambient air sampling involves collecting a representative sample of ambient air
for analysis. There are two general approaches: 1) “whole air” sampling with
canisters or Tedlar® bags and 2) “in-field concentration” sampling using sor-
bent tubes or cold traps. In this guide, we focus on collecting whole air sam-
ples in canisters, a flexible technique with many applications (Table I).

Passive vs. Active Sampling
In canister sampling, two sampling techniques are commonly used: passive
sampling and active sampling. Active sampling requires the use of a pumping
device whereas passive sampling does not.

In passive sampling, an air sample is pulled through a flow controller into an
evacuated canister over a chosen period of time, ranging from 5 minutes to 24
hours. The sampling period and the flow rate determine the canister volume
required. In active sampling, a pump is used to push the sample through a mass
flow controller and into the canister. Additional sample can be collected, relative
to the amount that can be collected by passive sampling, by pressurizing the can-
ister with sample. Commonly the sample is pressurized to 15 psig, effectively
doubling the sample volume.

Although active sampling is very flexible, a drawback to using a pump is the
need for additional quality assurance requirements for sample integrity (i.e., no
artifacts or loss of analytes). Additionally, a pump requires a battery or line
power source, which may be difficult in remote field-site sampling.

Grab vs. Integrated Sampling
If the environment is not changing, or if only a qualitative sample is needed, a
simple “grab” sample can be obtained. For example, an evacuated sample canis-
ter can be opened and sample rapidly collected at an uncontrolled rate, usually
over several seconds, until the container reaches equilibrium with atmospheric
pressure. Generally this qualitative approach is used when unknown analytes
must be identified, when the air contains high concentrations of analytes at cer-
tain (short) times, or when an odor is noticed and a sample must be obtained
quickly. Paired grab samples (before/after or smell/no smell) often are employed
to qualitatively diagnose a perceived problem.

To obtain a more representative sample requires time-integrated sampling. A
flow restrictor is used to spread the sample collection flow over a specific time
period to ensure an “average” composited or time-weighted average (TWA)
sample. A TWA sample will accurately reflect the mean conditions of the
ambient air in the environment and is preferred when, for regulatory or health
reasons, a typical exposure concentration is required for a situation that may
have high variability, as in an occupational setting.

II. Equipment Used for Passive Air Sampling
To ensure a valid sample when using a passive sampling technique, it is impor-
tant that the flow rate not change greatly during the time interval specified for
the integrated sample. The proper sampling equipment helps accomplish this
objective. A typical passive sampling train should include the following compo-
nents, all constructed of stainless steel: a sampling inlet, a sintered metal parti-
cle filter, a critical orifice, a flow controlling device, a vacuum gauge, and a can-
ister (Figures 1 and 2).

Figure 2 Integrated sampling kit.

sampling inlet

sample

canister

vacuum 

gauge

filter

flow 

controller

critical

orifice

rain cap

(1/8" or 1/4" nut)

Figure 1 Canister grab sampling kit.

Table I Canister applications.

Methods

US EPA TO-14A, TO-15; ASTM D5466 
OSHA PV2120; NIOSH Protocol Draft

Sampling Environment

Ambient air, indoor air, vapor intrusion, emergency response

VOC Range

<C3 to ~C10

Sampling Type

Grab & integrated sampling

Sensitivity

ppt to ppm

Sample

inlet

Fitting

with

orifice

10μm

Frit

Unassembled 

kit components

Assembled

kit on canister

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Sampling Inlet
The sampling inlet—the entrance to the sampling train—typically is cleaned
stainless steel tubing, either 

1/4" OD or 1/8" OD. US EPA Compendium Method

TO-14A/15 recommends sampling at a height of 2 meters above the ground. In
a highly trafficked area, this would minimize the problem of dust particles enter-
ing the sampling train. This height is not mandatory, however, and it is common
practice to use an inlet that is 12" (approximately 

1/3 meter) high. The EPA also

recommends having the entrance of the sampling inlet face downward to pre-
vent raindrops from entering the inlet. In some sampling trains, a 

1/8" or 1/4" nut

at the entrance of the inlet keeps water droplets away from the edge of the inlet,
where they could be drawn into the sampling train with the sample.

Particle Filter
The particle filter is installed in the sampling train prior to the flow-controlling
device to prevent airborne particles from entering the sample flow path.
Particles could partially obstruct the flow path and alter the flow rate during
sampling. In extreme cases, particles could plug the flow path and stop the sam-
ple flow. The smallest orifice commonly used in a passive sampling train is
0.0012" (approximately 30 micrometers). Without a particle filter, dust particles
could occlude this opening as they accumulate in the orifice fitting. Particles also
can affect the leak integrity of the valve, and possibly cause damage to the valve.

Two types of filters are used for this application, frit filters and in-line filters
(Figure 3). A variety of models of each type are available; most are of sintered
stainless steel and have 2-, 5-, or 7-micron pores. Use of smaller pore filters
reduces the likelihood of problems from airborne particles. EPA Compendium
Method TO-14A/15 recommends using a particle filter with 2-micron pores.

Critical Orifice
The critical orifice (Figure 4) restricts the flow to a specified range (Table II). In
conjunction with the flow controller, this allows the canister to fill at a certain rate
over a specified time period. The most common critical orifice design is a series of
interchangeable stainless steel 

1/4" NPT to 1/4" compression unions, each fitted with

a precisely bored ruby orifice. Each orifice provides a specific flow range (Table II).
Stability over a wide range of temperatures makes ruby the construction material
of choice. Typically during field sampling, the sampling train is subjected to tem-
perature fluctuations that would cause metals to contract or expand, affecting the
diameter of the aperture and thereby affecting flow. Ruby will not expand or con-
tract across ambient temperature extremes incurred during sampling.

A critical orifice can be used as the sole flow-restricting device, but it cannot
ensure uniform flow. Since the source pressure of the flow changes during
sampling, the flow rate through the orifice can also change, resulting in an
invalid time-integrated sample. It is important that a highly consistent flow
rate be maintained during passive sampling, and this is accomplished by the
flow controller.

Flow Controller
The flow controller (Figure 4) maintains a constant sample flow over the inte-
grated time period, despite changes in the vacuum in the canister, or in the envi-
ronmental temperature (Figure 5). In the Veriflo® Model SC423 XL Flow
Controller shown in Figure 4, the critical orifice acts as a flow restrictor,

Table II Critical orifice diameter vs. flow rate.

Orifice Diameter

Flow Rate Range

Canister Volume / Sampling Time

(in.)

(mL/min.)

1L

3L

6L

15L

0.0008

0.5–2

24 hr.

48 hr.

125 hr.

—

0.0012

2–4

4 hr.

12 hr.

24 hr.

60 hr.

0.0016

4–8

2 hr.

6 hr.

12 hr.

30 hr.

0.0020

8–15

1 hr.

4 hr.

8 hr.

20 hr.

0.0030

15–30

—

2 hr.

3 hr.

8 hr.

0.0060

30–80

—

—

1.5 hr.

4 hr.

0.0090

80–340

—

—

0.5 hr.

1 hr.

Figure 3 Filters used in sampling trains.

critical 

orifice

frit filter

stand 

alone in-line filter

Frit filter inside 

passive sampling kit

Figure 4 Flow controller & critical orifice.

atmospheric

reference

inlet

outlet

critical

orifice

adjustable

piston

diaphragm

Drawing courtesy of Veriflo Corp., 
a division of Parker Hannifin Corp.

spring

washer

in-line

filter

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upstream of a constant back pressure. This constant back pressure is established
by the balance between the mechanical spring rate of the diaphragm and the
pressure differential across the diaphragm. The latter is established by the pres-
sure difference between the atmospheric pressure, the vacuum in the canister,
and the flow through the critical orifice. The net result is a constant flow.

The critical orifice determines the flow range. The adjustable piston is used to
set a specific, fixed flow rate within the flow range. An adjustment to the posi-
tion of the piston changes the back pressure, which changes the pressure dif-
ferential across the critical orifice. If the piston is lowered away from the
diaphragm, the flow rate will increase. If the piston is raised toward the
diaphragm, the flow rate will decrease. This flow controller will accurately
maintain a constant flow despite changes in vacuum over a range of -30" Hg
to -7" Hg. Flow is constant until the vacuum range of the device is exceeded,
making the flow controller unable to maintain the constant pressure differen-
tial. In Figure 6, for example, the flow rate is constant from -29.9" Hg to
approximately -7" Hg, at which point the flow rate decreases because the flow
controller is unable to maintain the proper pressure differential. This control
will allow the user to collect approximately 5 liters of sample in a 6-liter canis-
ter. This is an extremely important factor in obtaining valid time-integrated
samples through passive sampling. We will discuss this point further in the
Field Sampling (Section V) of this guide.

Field Sampling and Laboratory Vacuum Gauges
A vacuum gauge as shown in Figure 7A enables sampling personnel to visually
monitor changes in the vacuum in the canister during sampling. If the flow rate
changes unexpectedly (e.g., due to a leak or an incorrect setting), the vacuum
gauge will indicate a disproportionately high or low vacuum in the canister, and
corrective action can be taken (i.e., flow adjusted) in time to ensure a valid sam-
ple. This type of vacuum gauge is attached to the sampling train for use in the
field. The vacuum gauge should be of high quality to ensure that it does not
introduce contaminants into the sample. All wetted parts in the vacuum gauge
are constructed of stainless steel; Restek gauges are accurate to within 1% of full
scale. Once used for sampling, a gauge must be cleaned, and should be certified
clean. Procedures are described later in this guide.

To monitor pressure in the canister before and after sampling, use a more accu-
rate measuring device. For example, test gauges built by Ashcroft®, as shown in
Figure 7B, are accurate to 0.25% of full scale. These sensitive gauges should not
be used in the field—they typically are wall mounted in the lab.

Courtesy of Veriflo Corp., a division of Parker Hannifin Corp.

Figure 6  A flow controller will maintain a constant sample flow
until it is unable to maintain a stable pressure differential across
the critical orifice.

Differential Pressure Response

Figure 7A Field Sampling Gauge

Figure 7B High Accuracy Laboratory Gauge

Figure 5  A flow controller will maintain a
constant sample flow despite changes in
canister pressure or environmental 
temperature.

Temperature Effects

Courtesy of Veriflo Corp., a division of Parker Hannifin Corp.

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Canister
The canister is a stainless steel vessel designed to hold vacuum to less than 10 mTorr or pressure to 40 psig.
Canisters are available in a range of volumes: 400 mL, 1.0 liter, 3.0 liter, 6.0 liter, and 15 liter. The size of can-
ister used usually depends on the concentration of the analytes in the sample, the sampling time, the flow
rate, and the sample volume required for the sampling period (Table II, page 3). Typically, smaller canisters
are used for more concentrated samples, such as soil gas collection, 3-liter and 6-liter canisters are used to
obtain integrated (TWA) ambient air samples at sampling times of up to 24 hours, and large 15-liter canis-
ters are used for reference standards. Sampling time will be limited by the combination of canister size and
the flow rate at which the sample is to be collected.

A well-designed canister is essential to the success of the sampling project. First, the canister should be
made of stainless steel, so the collected sample will not permeate through the vessel wall or degrade due
to exposure to light during shipment to the analytical laboratory. Second, the interior surface of the can-
ister should be inert, to reduce the potential for interactions with the analytes in the sample. Third, all can-
isters involved in a particular application should be of consistent volume, to simplify calculating sample
volumes. Finally, the canister should have a high quality valve that resists abuse in the field (e.g., over-
tightening that potentially could cause leaks). An inferior valve can fail, causing sample loss and incurring
replacement costs. It can be more expensive to sample again than to replace a valve.

Two types of canisters are available, the difference being the interior surface. The traditional canister is the
stainless steel SUMMA® or TO-Can® canister. The interior of this type of canister is electropolished, using
a polishing procedure (developed by Molectrics) that enriches the nickel and chromium surface and makes
it more inert than untreated stainless steel. The new generation of sampling canister is typified by the
SilcoCan® canister. Like the SUMMA® or TO-Can® canisters, the SilcoCan® canister is made of stainless
steel, and the interior is electropolished, but in an additional step—Siltek® treatment—an inert layer is
chemically bonded to the interior surface. Siltek® treatment makes the surface inert not only for relatively
inactive organic compounds, but also for compounds that are highly reactive with metal surfaces, such as
sulfur-containing compounds. Thus, surface inertness for SilcoCan® canisters exceeds that for SUMMA®
and TO-Can® canisters.

Canister Valve
The valve on a sampling canister must be of high quality, with the following characteristics: leak integri-
ty, a metal seat, stainless steel wetted surfaces, and a packless design. A metal seat eliminates offgassing of
seat components into the sample and memory effects in the seat material. A packless design provides a
completely enclosed system, to ensure no contamination from lubricants or packing material occurs.
Various valves are used, the most common being the Swagelok® SS4H bellows valve and the Parker
Hannafin diaphragm valve with metal seat. Several valve options are available for Restek canisters.

The connection of the valve to the canister is critical. The connection must be leak tight, to ensure a correct
sampling flow rate, but use extreme caution to prevent overtightening the tube compression fittings. To
ensure a leak tight valve, always use a pre-filter (such as an inline filter) to prevent valve seat damage.

Ensure Accurate Sampling of 
Reactive Compounds
with Siltek® Treatment

Siltek® treatment is a proprietary process, developed by Restek Corporation,
through which an inert layer is chemically bonded to a metal surface. The sur-
face produced by this treatment is virtually inert to active compounds. The
stainless steel pathway described in this guide is sufficient for sampling
atmospheres containing only nonreactive compounds, but for reactive com-
pounds the entire sampling pathway should be Siltek® treated to eliminate
contact between the reactive analytes and the metal surfaces. Siltek® treat-
ment can be applied to the interior surfaces of the canister and valve, to
ensure an inert sample pathway.

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III. Preparing the Sampling Train for Use
The sampling train must be prepared in the laboratory before it can be used in
the field. The train must be assembled and leak tested, the flow rate must be
set, and the train must be certified clean. All of the following information
should be documented for the chain of custody for the passive sampling train
and the sample collected with it.

Assemble, Leak Test, and Set the Flow Rate of the Passive Sampling Train
Choose the critical orifice (Table II, page 3) according to the sampling period
and flow rate you anticipate using (Table III). This will ensure an accurate and
valid sample. There should be a marking on the outside of the critical orifice fit-
ting indicating the size of the orifice. In a clean environment, assemble the sam-
pling train components as shown in Figure 2 (page 2). It is imperative that you
leak test the assembled train. If the sampling train leaks during sampling, the
final pressure in the canister will not be the desired final pressure, making the
sample invalid. The most common reason for invalid samples is leaks within the
sampling train. There are two ways to leak test the train:

1. Pass helium gas through the flow controller and use a sensitive helium

leak detector to test for leaks (e.g., Restek Leak Detector).

or…

2. Cap the inlet, attach the sampling train to an evacuated canister, open the

valve on the canister and evacuate the sampling train. Then, close the
valve and monitor any pressure change in the static sampling train. Leaks
of less than 1 mL/min. can be detected in 1-2 minutes.

This is a good practical test—the small internal volume of the passive sam-
pling train, combined with even a small leak, will produce a large change in
monitored pressure. According to EPA Method TO-15, the pressure change
should be less than 2 psig (13.8 kPa) over a 24-hour period.

After you are certain the sampling train is leak-free, set the desired sampling 
flow rate.

To set the desired flow rate follow these steps:
1. Remove the protective cap from the back of the Veriflo® Flow Controller

SC423XL body.

2. Connect either an evacuated canister or a vacuum source to the outlet of

the sampling train.

3. Connect a high quality calibrated flow meter (i.e., mass flow meter, rotame-

ter, GC-type flow sensor [e.g., Restek ProFLOW 6000 Electronic Flowmeter,
cat.# 22656]) to the inlet of the train.

4. Apply vacuum by opening the canister or turning on the vacuum source.

5. With a 3 mm hex (Allen®) wrench, adjust the piston gap screw to achieve

the desired flow rate (Table III). Between adjustments allow the flow to
equilibrate for several minutes. See Figure 8.

6. Replace the protective cap onto the back of the Veriflo® Flow Controller body.

Cleanliness: Certifying the Sampling Train for Use
US EPA Compendium Method TO-14A/TO-15 requires that the sampling
train be certified clean prior to use. Certify the train by passing a humidified,
high-purity air stream through the train, concentrating the exit gas on a trap,
and analyzing the gas by gas chromatography/mass spectrometry or other
selective detector. For the sampling train to pass certification the analytical sys-
tem should not detect greater than 0.2 ppbv of any target VOC.

The certified sampling train should be carefully packaged in aluminum foil or
in a clean container for storage or for shipment into the field. Care in packag-
ing is critical. Careless handling could affect the preset flow rate. When the
sampling train is ready for sampling, prepare the canister.

Figure 8  Setting flow rate on 
flow controller.

Important Precautions!
• Only hand tighten knob to close valve.

Overtightening may damage seat causing
leakage.

• Tighten compression fitting on valve inlet

only 

1/4 turn past finger tight.

Overtightening will cause leakage.

• Use prefilter during sampling to prevent

particulate damage to valve.

• Do not disassemble valve—disassembly may

void warranty.

• Protect valve inlet by replacing brass cap

when not in use.

• Do not exceed canister maximum pressure

of 40 psig.

Table III Flow rates for integrated sampling,
using a 6-liter canister and sampling on the
flat portion of the flow curve for the flow 
controller (Figure 5).

Sampling Period

Flow Rate Range

(hours)

(mL/min.)

0.5

133–167

0.75

89–111

1

67–83

2

33–42

4

17–21

8

8–10

12

5.6–6.9

16

4.2–5.2

24

2.8–3.5

125

0.5–0.7

Collected volume is 4–5 liters 
(flow = volume in mL / sampling time in min.).

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IV. Preparing the Canister for Sampling
Preparing a canister for sampling involves certifying the canister clean, evacuating the canister to final
pressure for use, and identifying the canister. All information acquired during these processes is needed
for the chain of custody.

Certifying the cleanliness of the canister is important toward ensuring that results reported are solely from
the site sampled, and not contaminated with residue from a previous site or volatiles in laboratory air. To
certify a canister clean, fill the canister with humidified air, pass the air from the canister through an adsor-
bent trap and analyze the adsorbent for target VOCs by GC/MS or other selective detector. Two US EPA
methods discuss canister certification: EPA Compendium TO-12 and EPA Compendium TO-14A/TO-15.
To comply with EPA Compendium Methods TO-14A/TO-15, the analytical system should not detect
greater than 0.2 ppbv of any target VOC. To comply with EPA Compendium Method TO-12 the analyti-
cal system, GC/FID, should not detect greater than 0.02 ppmC hydrocarbons. Although batch certification
of canister cleanliness is a relatively common practice, we recommend certifying and documenting each
canister individually. Detailed cleaning instructions are presented in Section VIII. Cleaning the Canister
(page 11).

Some laboratories certify a canister for VOC stability by introducing a low concentration test mixture into
the canister and measuring degradation over a specified time period. If the canister meets the specifica-
tion, it is certified for use. We recommend using such studies to ensure the effectiveness of a canister or
group of canisters for a proposed application.

Once the canister is certified clean, evacuate the canister to a final vacuum of 10-50 mtorr, using either the
canister cleaning system or a clean final vacuum system. This vacuum is critical to ensure the correct
amount of sample is collected. Use an accurate test gauge (shown in Figure 7b, page 4) or digital pressure
tester to ensure final vacuum has been reached and to document the final vacuum reading for the chain
of custody. Install a brass cap nut onto the canister valve to ensure no contamination can enter the sam-
ple pathway during shipment to the field.

Apply an individual identity to the canister, either with a label and serial number or with a bar code.

Some analysts prefer to introduce surrogate standards into the canister prior to sampling. Debate on this
practice revolves around theories that there are potential loss issues due to low humidity and inadequate
surface passivation by water. Neither Restek chemists nor our consulting experts recommend adding sur-
rogates to the canisters. If you choose to introduce surrogates into your canisters prior to sampling, be sure
to recheck and record the vacuum reading for each canister after adding the surrogates.

V. Field Sampling, Using a Passive Sampling Train and Canister
It is important to mention again that the sampling train and canister must be leak tested and certified
clean prior to use. To properly begin field sampling, we recommend bringing a “practice” evacuated can-
ister and a flow measuring device with you to the field. Use this canister to verify the flow rate through the
passive sampling train prior to using the train to obtain samples of record. To verify the flow rate, connect
the passive sampling train to the “practice” canister. Attach a flow meter to the inlet of the sampling train.
Open the canister and measure the flow rate through the sampling train. If the flow rate is within ± 10%
of the flow rate set in the lab, the train is ready to be used on the formal sampling canister. If the flow rate
is not within these limits, adjust the flow rate by adjusting the piston gap screw.

When the flow rate is confirmed, record the rate as the canister flow rate for the chain of custody form.

did you know?

Our light-weight tripod holds 
2 canisters securely without
any tools.

Pressure Conversion Table

Pressure

psi

atm

kg/cm

2

torr

kP

a

bar

inches Hg

psi =

1

0.068

0.0703

51.713

6.8948

0.06895

2.0359

atm = 

14.696

1

1.0332

760

101.32

1.0133

29.921

kg/cm

2 = 14.223

0.967

1

735.5

98.06 

0.9806

28.958

torr = 

0.0193

0.00132

0.00136

1

0.1330

0.00133

0.0394

kP

a = 0.1450

0.00987

0.0102

7.52

1

0.0100

0.2962

bar = 

14.5038

0.9869

1.0197

751.88

100

1

29.5300

in Hg = 

0.49612

0.0334

0.0345

25.400

3.376

0.03376

1

Multiply units in the left-most column by the conversion factors listed in the columns to the right.
e.g., 10PSI x 0.068 = 0.68atm, 10 bar x 29.5300 = 295.300 inches Hg

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To begin sampling, using the formal sampling canister, follow these steps:
1. Remove the brass cap nut from the canister valve.

2. If you are using a test gauge, attach the gauge to the canister and record the vacuum reading. If you choose not to use a test

gauge under field conditions, record the reading on the vacuum gauge that is part of the passive sampling train.

3. Attach the verified passive sampling train to the canister.

4. Record the sampling start time and necessary meteorological data.

5. Open the canister valve and begin sampling.

6. Periodically check the canister throughout the sampling period to ensure the pressure reading is accurate and sampling is pro-

ceeding as planned.

7. Once the sampling period is complete, close the valve and remove the sampling train. Check the final pressure within the canis-

ter, using the test gauge or the vacuum gauge in the sampling train.

There are four possible scenarios:

A. Ideally there will be a vacuum of -7"to -4" Hg in the canister (e.g., Table IV).

B. If more than -7" Hg vacuum remains, less sample was collected than ini-

tially anticipated. The sample will be valid, but the detection limit may be
higher than expected. You might have to pressurize the canister prior to
the analysis, which will dilute the sample and require you to use a dilution
factor to determine final concentrations of target compounds.

C. A vacuum of less than -4" Hg indicates the sample might be skewed

toward the initial part of the sampling period. This assumption usually is
valid because the flow rate through the flow controller will fall once the
vacuum falls below -5" Hg (Figure 6, page 4), when the change in pressure
across the flow controller diaphragm becomes too small and the flow con-
troller is unable to maintain a constant flow. Although flow was not con-
stant over the entire sampling period, the sample may be usable because
sample was collected over the entire interval.

D. If the ending vacuum is less than -1" Hg the sample should be considered

invalid because it will be impossible to tell when the sample flow stopped.

8. Record the final pressure in the canister and replace the cap nut.

Information that should be acquired at the sam-
pling site includes the start time and interval time,
the stop time, atmospheric pressure and tempera-
ture and, for ambient sampling, wind direction.
Include elevation if it is a factor. These parameters
often prove very useful when interpreting results.

After sampling, the canisters are sent back to the
laboratory where the final vacuum is measured
again with a test gauge. Using the initial vacuum
and final vacuum, the sample volume collected can
be determined from Equation 1.

It is also good practice to recheck the flow rate after
sampling, because this will affect the sample volume
(Equation 2). Laboratories typically allow a maxi-
mum deviation of ±10% to ±25% between the ini-
tial flow rate and the post-sampling flow rate.

Table IV Final vacuum and volume of 
sample collected in 6-liter canister.

Final Vacuum

Sample Volume

("Hg)

(liters)

29

0

27

0.58

25

0.99

23

1.39

20

1.99

17

2.59

15

2.99

12

3.59

10

3.99

7

4.60

5

5.0

3

5.40

0

6

Equation 2:
sample volume = [(initial flow rate + post-sampling flow rate)/2] x sampling time

Example: A flow controller was set at 3.3 mL/min. After obtaining a 24-hour
sample the flow rate was 3.0 mL/min.

sample volume = [(3.3 mL/min. + 3.0 mL/min.)/2] x 1,440 min. = 4,536mL

Equation 1:

pressure change*

sample volume =

x  canister volume

initial pressure

*initial pressure – final pressure

Example: A sample is collected in a 6-liter canister. The initial gauge pressure
reading when the canister left the lab was -29.92" Hg vacuum; the final gauge
pressure reading when the canister was returned to the lab was -7" Hg vacuum.

-29.92" Hg – (-7" Hg)

sample volume =

x  6 L = 4.59 liters collected

-29.92" Hg

9

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VI. Analysis of Collected Samples
Once received by the lab, each canister is identified from the information in the
chain of custody report. The final pressure is checked to ensure no leaks
appeared during transport. It might be necessary to pressurize a canister prior
to the analysis; do this by adding humidified nitrogen or air to the canister to
a pressure greater than 5 psig or higher, depending on the sample volume
needed for analysis or for suitably diluting the sample (e.g., Table V). The need
to dilute is determined by the preconcentrator instrument. Some air precon-
centrators can be operated while the canister is under slight vacuum. Check
with your instrument manuals or with the manufacturer to determine if you
must dilute your samples prior to analysis. Dilution factors can be calculated
according to Equation 3.

To analyze the sample, withdraw an aliquot of the sample from the canister. For low level ambient air analysis, withdraw 250-500 mL
of sample from the canister and concentrate the analytes by using a mass flow controller and a cryogenically cooled trap (e.g., glass
beads and/or a solid sorbent). Desorb the concentrated analytes from the trap and deliver them to a cryofocuser to focus the sample
bandwidth prior to introduction onto the GC column. A 60 m x 0.32 mm ID x 1.0 µm Rtx®-1 column typically is used for EPA
Method TO-14A or Method TO-15 ambient air analysis; an MSD is a common detector. Figure 9 shows a typical TIC spectrum for
a TO-15 ambient air analysis.

Table V Dilution factors to adjust final
sampling pressure to 14.7 psig for a 
6-liter canister.

Final Vacuum

Sample Volume

Dilution

("Hg)

(liters)

Factor

29

0

63.77

27

0.58

20.37

25

0.99

12.12

23

1.39

8.63

20

1.99

6.02

17

2.59

4.63

15

2.99

4.01

12

3.59

3.34

10

3.99

3.00

7

4.60

2.61

5

5.0

2.40

3

5.40

2.22

0

6

2.00

Equation 3:
dilution factor = (Pafter dilution + Plab atmosphere) / (Plab atmosphere - Pbefore dilution)

The dilution factor is calculated from the post-sampling pressure (before dilu-
tion), the final pressure (after dilution), and the atmospheric pressure in the lab-
oratory. The factor for converting "Hg to psi = 0.491.

Example: At the end of a sampling period the gauge pressure in a canister was
-7 "Hg. The canister was pressurized with nitrogen to 14.7 psig (1 Atm.).

The dilution factor is (14.7 + 14.7) / (14.7 - (7 x 0.491)) = 2.61

Figure 9 US EPA TO-15 ambient air analysis.

Column:

Rtx

®-1, 60m, 0.32mm ID, 1.0µm (cat.# 10157)

Sample:

TO-15 standard (cat.# 34436) humidified to 33% RH in a 6L SilcoCan®
canister (cat.# 24182)

Concentrator:

Nutech 3550A Preconcentrator; 300mL sample concentrated at 
-160°C, thermally desorbed at 150°C, cryofocused at -185°C, 
thermally desorbed to column at 150°C

Carrier gas:

helium, constant flow

Flow rate:

1.2mL/min.

Oven temp.:

30°C (hold 4 min.) to 175°C @ 8°C/min., to 220°C @ 
20°C/min. (hold 2 min.)

Det.:

MS

Transfer line

temp.:

150°C

Scan range:

35–280amu

Ionization:

EI

Mode:

scan

1. propylene
2. Freon

®-12 (dichlorodifluoromethane)

3. chloromethane
4. Freon

®-114 (dichlorotetrafluoroethane)

5. vinyl chloride
6. 1,3-butadiene
7. bromomethane
8. chloroethane
9. carbon disulfide

10. acetone
11. Freon

®-11 (trichlorofluoromethane)

12. isopropyl alcohol
13. 1,1-dichloroethene
14. methylene chloride
15. Freon

®-113 

(1,1,2-trichloro-1,2,2-trifluoroethane)

16.

trans-1,2-dichloroethene

17. 1,1-dichloroethane
18. methyl 

tert-butyl ether

19. vinyl acetate
20. methyl ethyl ketone
21.

cis-1,2-dichloroethene

22. hexane
23. chloroform
24. ethyl acetate
25. tetrahydrofuran
26. 1,2-dichloroethane
27. 1,1,1-trichloroethane
28. benzene
29. carbon tetrachloride
30. cyclohexane
31. 1,2-dichloropropane
32. trichloroethylene
33. bromodichloromethane
34. 1,4-dioxane
35. heptane
36.

cis-1,3-dichloropropene

37. methyl isobutyl ketone

38.

trans-1,3-dichloropropene

39. 1,1,2-trichloroethane
40. toluene
41. methyl butyl ketone
42. dibromochloromethane
43. 1,2-dibromoethane
44. tetrachloroethylene
45. chlorobenzene
46. ethylbenzene
47.

p-xylene

48.

m-xylene

49. bromoform
50. styrene
51.

o-xylene

52. 1,1,2,2-tetrachloroethane
53. 4-ethyltoluene
54. 1,3,5-trimethylbenzene
55. 1,2,4-trimethylbenzene
56. 1,3-dichlorobenzene
57. benzyl chloride
58. 1,4-dichlorobenzene
59. 1,2-dichlorobenzene
60. 1,2,4-trichlorobenzene
61. hexachloro-1,3-butadiene

GC_AR00748

10

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Procedures used in these chromatographic analyses generally include a multi-
point calibration, using gas standards. Therefore calculations of organic com-
pounds in collected samples are straightforward—only volumes analyzed and
dilution rates are needed to determine sample concentrations. High concen-
tration calibration gas standards are commercially available (e.g., 1 ppmv or
100 ppbv). To prepare analytical standards, introduce an aliquot of stock mate-
rial into a canister and dilute with humidified air or nitrogen. After analyzing
the calibration standards, determine the response factor for each analyte using
the peak area counts per concentration.

After analyzing the multipoint calibration standards and calculating peak
area/concentration response factors, analyze the “real world” samples. If an
“unknown” sample has not been diluted, apply the corresponding response
factor to each “unknown” analyte peak area to get the reporting limit concen-
tration of the “unknown” in the analysis (typically in ppbv). If you have dilut-
ed the canister to get a positive pressure, you must apply the dilution factor to
the concentration values. This is done by multiplying the reporting limit by the
dilution factor.

VII. Cleaning the Passive Sampling Train
The cleanliness of the sampling train is critical to collecting accurate and rep-
resentative samples. Practices followed for cleaning passive sampling equip-
ment between uses range from purging the sampling pathway with humidified
nitrogen or air for many hours, to heating the pathway during a purge, to dis-
assembling each component, sonicating the pieces in solvent (except for the
critical orifice), and oven baking the pieces prior to reassembly. The most
suitable mode of cleaning depends on the concentrations of analytes of inter-
est, and contaminants, in the previous sample collected.

The particle filter must be thoroughly cleaned between uses. Disassemble the
filter, then remove the larger particles from the frit by blowing particle-free
nitrogen through the frit from the outlet surface toward the inlet surface. After
the larger particles are removed, sonicate or rinse the filter parts in methanol
and then bake the parts in an oven at 130 °C to remove any residual organic
vapors.

The critical orifice and flow controller can be cleaned in either of two ways.
The first method is to disassemble the flow controller and clean all the metal
parts with methanol. This will remove any high boiling point compounds that
have condensed onto the wetted areas of the controller. Heat the cleaned parts
in an oven at 130 °C to remove residual organic vapors. Do not sonicate the
critical orifice. Do not sonicate in solvent or bake any of the nonmetallic
parts, such as O-rings, or they will be damaged. Do not rinse the vacuum
gauge with methanol. The vacuum gauge may be heated, but do not exceed 80
°C; higher temperatures will damage the face and the laminated safety glass
lens. Heating to 80 °C will not affect the mechanical operation of the spiral
bourdon tube in the vacuum gauge.

A less involved method of cleaning the flow controller is to use a heating jack-
et or heat gun to heat the components of the assembled sampling train, while
purging the system with nitrogen. As organic compounds are heated and des-
orbed from the interior surfaces, the nitrogen gas sweeps them out of the sam-
pling equipment.

Preparing the Clean Passive Sampling Train for Re-use
After the sampling train components have been cleaned, reassemble the sys-
tem, check for leaks, set the desired flow rate, and certify the sampling system
clean. Follow the procedures described previously in this guide. Package the
clean sampling train to prevent contact with airborne contaminants.

frequently asked question

Where can I find EPA 
Air Toxic Methods?

pdf files of US EPA Air Toxic 
Methods are available at this 
web address: 
www.epa.gov/ttn/amtic

for more info

ASTM Reference D5466 Standard 
Test Method for Determination 
of Volatile Organic Chemicals in
Atmospheres (Canister Sampling Methodology)

available at www.astm.org

11

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VIII. Cleaning the Canister
Every air sampling canister, whether new or used, must be cleaned and certified before it is used for sam-
pling. Some laboratories batch test and certify canisters. This is done by testing and certifying one canis-
ter out of 10 following cleaning. We recommend certifying each canister clean prior to use—especially if
there is potential for litigation.

For years there has been much discussion regarding what constitutes a proper procedure for cleaning can-
isters. US EPA Method TO-15 has provided guidance, and in the last 5–10 years automated commercially
available canister cleaning systems have evolved. Because many of these systems are quite expensive, and
some designs have limitations, analysts often design their own systems and methodologies for cleaning can-
isters. The cleaning procedure described in this section is a practical approach that will ensure canisters are
suitably cleaned for ambient air sampling, whether you are using a commercially available cleaning system
or a system of your own design. There are minor differences when cleaning SilcoCan® or TO-Can®
(SUMMA®) canisters. We will discuss these differences in this procedure.

Air Versus Nitrogen
The two gases recommended for cleaning canisters are humidified ultra-high purity air and ultra-high
purity nitrogen. The water in the humidified gas hydrolyzes impurities in the canister and, according to
theory, will occupy the active sites on the interior surface, displacing the impurities and allowing them to
be removed. Air is recommended when oxidation of the interior surface is desired. The oxygen content of
air, 21%, is sufficient for this surface oxidation; it is not necessary to use pure oxygen gas. Nitrogen is
equally effective for cleaning ambient air canisters, but will not oxidize the surface of the canister.

Heat or No Heat*
Some user-designed canister cleaning systems do not heat the canisters. Typically this does not create a
problem when cleaning canisters that are used in ambient air collection, but as a safeguard we recommend
heating the canisters during the cleaning process. Compounds collected in most ambient air samples are
in the low ppbv range, and can be removed from a canister by multiple cycles of pressurization with
humidified air or nitrogen followed by evacuation. If there are higher concentrations of contaminants in
the canister, heat might be required to clean the canister satisfactorily. In addition, the cleaning cycle may
be reduced when heat is applied.

Caution: Adding heat and humidified gas to a canister may create a steam pressure vessel. Some commercial cleaning systems
incorporate a pressure release valve to ensure the pressure does not exceed the pressure rating of the canisters.

Cleaning Systems

• Oven Some canister cleaning systems are incorporated within an oven. Batch size is determined
by the number of canisters that can fit inside the oven. The supply line for the humidified air or
nitrogen stream and the line to the vacuum system are plumbed directly into the oven. A cold trap
is employed to trap impurities. Accurate monitoring of vacuum and pressure is required. In this
arrangement, the entire canister, including the valve, will be heated. This will help remove contam-
inants if both the valve and the canister are dirty. Typically, when using heat, it is helpful to create
steam from the humidified air or nitrogen stream. An oven temperature of at least 120 °C is
required, but higher temperatures often are used.

• Heat Bands A band heater placed around the equator of the canister typically is capable of heat-
ing the canister to approximately 130 °C. There is a heat gradient, and the valve might only receive
radiant heat (approximately 70–100 °C). In most sampling situations, this lower temperature
should be sufficient for effectively removing contaminants from the valve.

• Insulated Heat Jackets Insulated heat jackets surround and heat each canister. These jackets
typically have a silicone or 

PTFE-coated fiberglass fabric exterior and a fiberglass insulation inte-

rior. Some operate at a fixed temperature; others can provide variable temperature. Restek’s heat-
ing jacket offers a significant advantage over alternatives because it encompasses the valve area.

• Infrared Heat An infrared heating system includes an infrared heat source and a reflective panel
similar to the cylinder drying rack on a gas cylinder system. The infrared source and the reflective
panel are placed on opposing sides of the canisters. Infrared rays from the source heat the canisters;
rays that pass the canisters strike the reflective panel and heat the canisters from the opposing side.

• User Designed Figure 10 shows an example of a “homemade” system designed to clean 24 six-
liter canisters. This design does not employ heat, but a heater can be added (see Heat or No Heat).
It provides a humidified air or nitrogen stream to all canisters and the roughing pump on the bot-
tom shelf is the vacuum source. This system is computer operated to automate the cleaning cycles.

*If you are cleaning any fused
silica lined canisters, and will
be using heat, use humidified
nitrogen, not air.

Cleaning any fused silica lined
canisters with humidified air
and heat above 80 °C may
damage the fused silica sur-
face, resulting in reduced
recoveries of sulfur and other
reactive compounds.

Air Canister 

Heating Jacket

TO-Clean Canister
Cleaning System

Figure 10

User-designed system 

for cleaning 24 

six-liter canisters.

12

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Cleaning Method
1. Connect all canisters to the cleaning system, then release any pressure within any of the

canisters. 

Apply vacuum to the system to evacuate the canisters. US EPA Method TO-14A/15 rec-
ommends evacuating the system to 50 mTorr for 1 hour, but a reduced pressure of -23
to -25 " Hg is sufficient for general cleaning.

2. After the canisters have been under vacuum for approximately 1 hour, pressurize the

canisters with humidified air or nitrogen*. Pressurization will dilute the impurities and
the moist air will hydrolyze them. 

Pressurize canisters to 5 psig if they will be heated, or to 30 psig if they will not be heated.

Proceed to step 3 when the system has equilibrated at the designated pressure.

3. Heat the pressurized canisters to 120–250 °C, depending on the type of valve on the

canister being cleaned. Different valves have different temperature limits; consult the
manufacturer specifications for your valve type. Many commercial cleaning systems
avoid this concern by ensuring the valve is not within the heated zone. The canister
below the valve is heated but the valve receives only radiant heat.

Heat the canisters filled with humidified air/nitrogen for at least 1 hour.

4. Re-evacuate the canisters to remove the desorbed impurities. 

Allow the canisters to equilibrate for 1 hour. 

5. Determine if the canisters have been cleaned effectively by following the procedure in

Certifying the Canister (p. 13). US EPA methods recommend testing every canister until a
reliable procedure is developed.

Repeat steps 1–5 as necessary; the number of cycles will be determined by how dirty
the canisters are and how easily they are cleaned. 

We recommend developing a cleaning procedure that matches your specific sampling
procedure, by testing the canisters for cleanliness after each cycle and determining the
number of cycles necessary for proper cleaning. 

If the canisters are not heated, the number of cycles required to clean the canisters
might be higher.

6. Once a canister is clean, prepare it for collecting a sample by evacuating it to 10–50

mTorr. If your system is leak-tight, you can do this by using a roughing pump. 

Many commercial systems include a molecular drag pump to reach final vacuum quickly.

*If you are cleaning any fused silica lined canisters, and will be using heat, use humidified nitrogen, not air.

Cleaning any fused silica lined canisters with humidified air and heat above 80 °C may damage the fused silica surface,
resulting in reduced recoveries of sulfur and other reactive compounds.

Figure 11 Aliquots from a canister before and after cleaning with 2 cycles of humidified air while heated to 200 °C.

13

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IX. Certifying the Canister
We recommend certifying canisters for both cleanliness and for analyte stability. To certify a canister clean,
pressurize the canister to 14.7 psig with humidified ultra-high purity air or nitrogen after it has gone
through the cleaning cycles. The humid air or nitrogen stream must be certified clean before it can be used
for canister certification. Analyze an aliquot of the canister content by GC/MS or GC/FID/ECD. US EPA
Method TO-14A/15 specifies a canister must contain less than 0.2 ppbv of any target VOC compound
(Figure 11); EPA Method TO-12 specifies less than 0.02 ppmC, as detected by GC/FID. If a canister does
not meet specification, it must be cleaned again and retested for certification.

To certify a canister for analyte stability, introduce a low working concentration of a characterized test mix
into the canister. Analyze an aliquot of the contents of the canister immediately after introducing the test
mixture and at periodic intervals. We recommend monitoring for changes for a minimum of 2 weeks or
for a timeframe similar to your anticipated holding period. Responses should not decrease more than 20%
over this period.

Commercial standards are available for stability testing, but we recommend you make your own test mix-
ture that is comparable to the target compound list that the canister will hold. For example, if you are ana-
lyzing sulfur compound content in ambient air, prepare a sulfur-specific test mix and evaluate the canis-
ter’s performance for sulfurs. Maintain a log sheet for each canister, and record the test results and certi-
fication. This will be a permanent record for each canister. Some labs certify canisters for certain com-
pounds and use a canister only for this specific application.

Dirty can

Clean can

Rtx®-1 60m x 0.32mm ID x 1.0µm (cat. #10157); 50°C (hold 1 min) to 165°C @ 8°C/min. to 220°C @ 15°C/min. (hold 5 min.); flow rate = 1.4mL/min.; Nutech 3550 Preconcentrator 
conditions: sample= 300cc from canister, cryotrap = -160°C, desorb = 150°C, cryofocuser = -190°C, desorb = 150°C; MSD conditions: Instrument: HP5971 GC/MSD, 5 minute sol-
vent delay, scan range = 25-260amu

14

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X. Conclusion
A well designed and properly prepared passive sampling system helps ensure accurate, useful information is obtained from an air
sampling project. In this guide, we describe the components of the system, procedures for assembling the system and preparing it for
sampling, and the sampling procedure. Cleaning system options and procedures for cleaning a used sampling train and canister for
certification prior to a subsequent sampling are also presented. The following section describes Restek products designed to help col-
lect and analyze air samples.

How to Extend Canister Life
What reduces canister performance and longevity? Leakage is the most common reason for canister failure, but contamination 
and damage to the fused silica lining can also send canisters to the scrap yard prematurely. Here are some tips to protect your
investment:

1. Prevent leaks

Use proper handling to avoid these 3 leading causes of leaks.

a. Particles in the valve

You can prevent particles from entering the valve by always using a 2 or 7 µm particulate filter during sampling and on your

canister cleaning equipment. Also, protect the valve inlet by replacing the brass dust cap when not in use. The EPA-recom-
mended metal-to-metal sealing valves provide the greatest inertness, but tend to be more sensitive to particulate damage
than other valve types.

b. Galled thread fittings

Avoid galled thread fittings by using a gap gauge to prevent overtightening of compression fittings. Turning only ¼ turn
past finger-tight is another rule of thumb to prevent overtightening. Use brass compression fittings on stainless steel, dur-
ing nonsampling activities, such as cleaning or calibration, to minimize thread damage. Galled threads may also cause a
poor connection to vacuum/pressure gauges, resulting in inaccurate measurement and misleading conclusion that canis-
ter leakage exists.

c. Overtightened valve

Canister valves are designed to close securely with hand tightening only. Overtightening a valve closure with a wrench may
damage the valve seat where the seal is made.

2. Reduce contamination

a. Segregate high concentration (ppm) cans and trace concentration (ppb) cans. Use dedicated canisters, or gas sam-

pling bags, for ppm level sampling, since it is extremely difficult to remove impurities from ppm sampling to a level
suitable for trace sampling.

b. Clean the entire sampling train as you would the can to minimize introduction of contaminants into a clean can.

Maximum temperature is 80 °C on the gauge and 90 °C on Restek’s Veriflo® flow controller.

c. High temperature (>100 °C) humidified air (steam cleaning) provides the most effective way to remove contamination

from electropolished cans (TO-Can® or SUMMA® canisters), but can damage fused silica lined cans. See #3 below for
proper cleaning of fused silica lined cans.

3. Avoid damage to fused silica lined cans

Be sure to follow method recommendations when cleaning your canisters to avoid damaging the fused silica lining. Cleaning
studies of SilcoCan® canisters using humidified air and heat at 80 °C and 125 °C have shown reduced recoveries of sulfur com-
pounds, when compared to using nitrogen under the same conditions. This irreversible damage is due to oxidation of the
surface, creating active sites that may affect the recovery of reactive or polar compounds. Strong acids and bases may also
result in damage to the internal can surface.

SilcoCan® Air Monitoring Canisters

Restek Exclusive!

15

 www.restek.com

XI. Air Sampling Products

also available

We also offer sampling kits, sampling bags, and 
a range of gas reference standards to meet your
environmental gas sampling requirements. 
See www.restek.com/air

Quickly confirm vacuum or pressure. 

Request a high-quality gauge mounted 

on your SilcoCan® or TO-Can® canister.

• Get high performance canisters from the innovators of fused silica coating

technology.

•  Variety of options available, including SUMMA can equivalent.
• Standard fittings compatible with all instrumentation and accessories.
• Exclusive manufacturer of 1L spherical canister.
• Repair service available to extend canister life.

Canister Options

Sizes

1, 3, 6, 15L

Valves

Parker diaphragm, Swagelok bellows

Interior Coating

Electropolished, Siltek treated

Gauges

3 vacuum/pressure ranges

Applications

Ambient Air - US EPA TO-14A, TO-15, ASTM D5466
Indoor Air
Vapor Intrusion
Emergency Response

Air Canisters for VOC Monitoring

See our complete line of products for

Air Monitoring

visit www.restek.com/air

1L Volume

3L Volume

6L Volume

15L Volume

Description

qty.

cat.#

cat.#

cat.#

cat.#

SilcoCan Canister,

1/4" Valve

ea.

24180

24181

24182

24183

SilcoCan Canister,
Siltek Treated 

1/4" Valve

ea.

24180-650

24181-650

24182-650

24183-650

SilcoCan Canister
with Gauge, 

1/4" Valve

ea.

24140

24141

24142

24143

SilcoCan Canister with Gauge

**,

Siltek Treated 

1/4" Valve

ea.

24140-650

24141-650

24142-650

24143-650

SilcoCan Canister
without Valve

ea.

22090

22091

22092

22093

SilcoCan® & TO-Can® Air Monitoring Canisters

Can

Dimensions

Volume

(height x sphere diameter)

Weight

1 liter

8.5 x 5.25"

21.6 x 13.3cm

2.5 lbs

1.13kg

3 liter

11.5 x 7.25"

29.2 x 18.4cm

4 lbs

1.81kg

6 liter

12.5 x 9.25"

31.8 x 23.5cm

7 lbs

3.18kg

15 liter

17 x 12.25"

43.2 x 31.1cm

13 lbs*

5.90kg

*16 lbs shipped UPS Air, 22 lbs shipped Fed Ex (USA).

1L Volume

3L Volume

6L Volume

15L Volume

Description

qty.

cat.#

cat.#

cat.#

cat.#

TO-Can Canister with 

1/4" Valve

ea.

24172

24173

24174

24175

TO-Can Canister with Gauge

**, 1/4" Valve ea.

24176

24177

24178

24179

TO-Can Canister without Valve

ea.

22094

22095

22096

22097

24182

22107

TO-Can® Air Monitoring Canisters

TO-Can Canister with 

1/4" Swagelok

SS4H Bellows-Sealed Valve

ea.

22105

22106

22107

22108

SilcoCan® canisters effectively store very low levels of 
sulfur compounds.

Dry SilcoCan® (n=18)
Humidified SilcoCan® (n=5)
Electropolished (n=2)

●
◆

▲

Time (Days)

Percent Recovery

11 ppbv H2S

**range of standard gauge is -30" Hg to 60 psi.

16

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Restek

Entech

Capacity

12-6L cans

6-6L cans

Software

Included

Separate

www.restek.com/air

Air Canister Tripod conveniently 

holds 2 air canisters.

TO-Clean Canister Cleaning System
High capacity, fully automated, easy to use canister cleaning oven dramati-
cally increases lab efficiency.

• Twelve 6L canister capacity; custom-built trays for different canister sizes.
• Method TO-14A/15 compliant.
• Small footprint saves lab space.
• No computer needed—uses embedded touch screen controller.
• Save up to 10 user defined methods.
• Automated system leak test.
• Isothermal oven cleans entire can AND valve more completely than band

heaters.

• Includes Edwards® RV-8 vacuum pump—no turbo pumps!
• One year limited warranty.

Shipping: FedEx Ground, unless otherwise requested. Costs vary depending on ship-to location.

Note: Ovens are built on demand, therefore, a ten week lead time is required on all orders. A limit-
ed cancellation and return policy applies to TO-Clean ovens; contact Restek Customer Service for
details. Not available in countries requiring CE certification (Europe & Japan).

Description

qty.

cat.#

TO-Clean Oven, 120V, 60Hz

ea.

22916

TO-Clean Oven, 220/230V, 50/60Hz

ea.

22917

Optional Accessories (not included with TO-Clean Oven)

qty.

cat.#

Dewar, glass, 4300mL stainless steel u-tube trap

ea.

22918

Oven Cart, 29"H x 27"W x 49"D, 12 gauge steel, push handle and casters

ea.

22919

1L Option: includes tubing, fittings, and inserts for 24 1L canisters

ea.

22920

Humidification Chamber

ea.

24282

Dimensions:  
44"H x 48"W x 27"L
Weight: 525 lbs

Air Canister Tripod
• Lightweight (9 pounds) and compact, for easy storage and transport.
• Extends from 6' to 9' high.
• Large base provides enhanced stability, without additional supports.
• Sturdy, rugged metal design, for outdoor sampling and transport.

Restek’s Air Canister Tripod holds two canisters simultaneously for collocated
ambient air sampling. The custom-designed bracket holds most 1 L, 3 L, and
6 L canisters securely, without any tools.*

Description

qty.

cat.#

Air Canister Tripod

ea.

24151

*Air sampling canisters sold separately.

Whether automated or manual, Restek’s Canister Timer 

has the features you need for easy, reliable sampling!

Simplify Air Sampling

Canister Air Sampling Timer
• Program up to 12 timed events!
• Capable of both manual and automated operation.
• Perfect for either grab or time-integrated sampling.
• Long battery life; recharges conveniently using the USB port on any PC.
• All stainless steel sample flow path ensures inertness, improving accuracy.

Description

qty.

cat.#

Canister Air Sampling Timer

ea.

24267

17

www.restek.com

Get Mini!

Mini-Can Options

Sizes 

400cc, 1000cc

Valves

Quick connect, diaphragm

Interior Coating

Electropolished, Siltek treated

Sample Inlets

Area, personal

Flow ranges

0.5-15 sccm

Mini-Can Stand

Sampling Belt &

Personal Sample Inlet

• Grab and integrated sampling without sampling pump.
• 8-hr integrated sample possible with 400 cc mini-can.
• Siltek® coating delivers high level of inertness for H2S & other

reactive compounds.

• Versatile enough for many applications: 

-  Indoor air

-  Industrial hygiene

-  Soil gas

-  Emergency response

For more information on Restek’s

Mini-Cans, sampling kits, 

and accessories, visit

www.restek.com/air

Expand Air Sampling with
Mini-Cans & Accessories

Miniature Air Sampling Kits
• Provide accurate integrated sampling without a sampling

pump.

• Convenient smaller size connects easily to miniature canisters.
• Available in stainless steel or Siltek® treated components for

greater inertness.

Restek’s passive air sampling kit incorporates all the hardware
necessary to collect air samples, and is easy to assemble for field
sampling.* Kit includes flow controller, critical orifice, 2 µm frit
filter, vacuum gauge, and sample inlet. The gauge (cat.# 24120)
and sample inlet (cat.#s 26211, 26212) are downsized for part-
nering with smaller canisters.

*Air sampling canisters sold separately.

Canister

Flow

Orifice

Siltek Treated Stainless Steel

400cc

1 Liter

(sccm)

size

Sampling Kits

Sampling Kits

8 hour

24 hour

0.5–2

0.0008"

26253

26252

2 hour

4 hour

2–4

0.0012"

26255

26254

1 hour

2 hour

4–8

0.0016"

26257

26256

—

1 hour

8–15

0.0020"

26259

26258

Miniature Air Sampling Kits

Miniature Air Sampling Canisters

400cc

1,000cc

Description

qty.

cat.#

cat.#

Miniature Canister with Quick-Connect Stem Fittings

Electro-Polished Stainless Steel

ea.

24188

24194

Siltek Treated

ea.

24189

24195

Siltek Treated,  with  Siltek Treated  Quick-Connect
Stem Fitting

ea.

24190

24196

Miniature Canister with Metal-Seated Diaphragm

Electro-Polished Stainless Steel

ea.

24191

24197

Siltek Treated

ea.

24192

24198

Siltek Treated, with Siltek Treated Diaphragm Valve

ea.

24193

24199

Mini-Can Accessories
These accessories enhance the usage of the mini-can and
provide flexibility in their application, from personal to
area to vapor intrusion sampling.

Description

qty.

cat.#

Sampling Belt

ea.

22122

Personal Sample Inlet (includes: 3" x 

1/16" OD 

PTFE tubing,

Clip, 

PTFE Reducing Ferrule, 1/4" SS nut)      

                  ea.           22123

Mini-Can Stand

ea.

22124

18

www.restek.com

Includes:

1 Veriflo® SC423XL flow controller
2 Stainless steel vacuum gauge
3

1/4-inch Siltek® sample inlet

4 2-micron frit filter and spring 

washer (not visible in image) 

5 Interchangeable critical orifice

Superior Performance—an Excellent Restek Value
Integrated Air Sampling Kits
• Provide accurate integrated sampling without a sampling pump.
• Inert Siltek® treated components ensure accurate sampling of active 

components.

• Excellent for sampling times from 0.5 hour to 125 hours.

Restek’s passive air sampling kit incorporates all the hardware necessary to col-
lect air samples, and is easy to assemble for field sampling.* The improved fil-
ter design greatly reduces the number of potential leak sites.

The passive air sampling kit is available in seven sampling flow ranges, and in
stainless steel or Siltek® treated finish. The stainless steel kit is ideal to partner
with the Restek TO-Can® air sampling canister for TO-14A and TO-15 meth-
ods. Use the Siltek® treated version with the Restek SilcoCan® air sampling
canister when collecting low-level volatile sulfur compounds, or other active
compounds.

*Air sampling canisters sold separately.

Canister Volume*/Sampling Time

Flow

Orifice

Siltek Treated

Stainless Steel

400cc

1 Liter

3 Liter

6 Liter

15 Liter

(sccm)

size

Sampling Kits

Sampling Kits

8 hour 24 hour 48 hour

125 hour

—

0.5–2

0.0008"

24217

24216

2 hour 4 hour

12 hour

24 hour

60 hour

2–4

0.0012"

24160

24165

1 hour 2 hour

6 hour

12 hour

30 hour

4–8

0.0016"

24161

24166

—

1 hour

4 hour

8 hour

20 hour

8–15

0.0020"

24162

24167

—

—

2 hour

3 hour

8 hour

15–30

0.0030"

24163

24168

—

—

—

1.5 hour

4 hour

30–80

0.0060"

24164

24169

—

—

—

0.5 hour

1 hour

80–340

0.0090"

22101

22100

2

3

5

1

4

Canister Grab Sampling Kit
• Use with 1, 3, or 6 L canisters, for qualitative grab air sampling.
• 1/4" compression fitting connects directly to canister valve inlet.
• Replaceable frit protects orifice and valve from particulates.
• Sample inlet design minimizes water entry into sampling train.
• Variety of orifice sizes, for fast sampling from 5 to 60 minutes.
• Individual replacement components available.

*Air sampling canisters sold separately.

Replacement Fittings for Grab Sampling Kits

Siltek Treated

Stainless Steel

Replacement Fitting w/Orifice

Replacement Fitting w/Orifice

Orifice Size

cat.#

cat.#

0.0018"

26288

26271

0.0020"

26289

26272

0.0030"

26290

26273

0.0040"

26291

26274

0.0055"

26292

26275

0.0080"

26293

26276

0.0090"

26294

26277

0.0130"

26295

26278

Sample

Inlet

Fitting

with

orifice

10μm

Frit

Unassembled 

kit components

Assembled

kit on canister 

(canister sold separately)

Siltek Treated

Stainless Steel

Canister Volume*/Sampling Time (min.)

Flow

Grab Sampling Kits Grab Sampling Kits

1 L Canister 3 L Canister 6 L Canister (mL/min.) Orifice Size

cat.#

cat.#

60

—

—

15

0.0018"

26280

26263

30

—

—

20

0.0020"

26281

26264

15

60

—

45

0.0030"

26282

26265

—

30

60

80

0.0040"

26283

26266

5

15

30

150

0.0055"

26284

26267

—

—

15

300

0.0080"

26285

26268

—

5

—

390

0.0090"

26286

26269

—

—

5

>1,000

0.0130"

26287

26270

19

 www.restek.com

Gas Standard Accessories

Canister and passive air sampling kit 

must be purchased separately.

• Standards from TWO manufacturers provide 

second source on one order.

• 12 month stability in transportable cylinders.
• Drop shipped for fast delivery and maximum shelf life.

2nd Source

TO-14A/TO-15 Gas

Calibration Standards 

For more available gas standards,

visit www. restek.com/air

A. Spectra (Linde) 

104L Cylinders

B. Scotty (Air Liquide) 

110L Cylinders 
(Pi-marked Cylinders 
for EU Regulations)

B. 

NEW!

Naphthalene now

added to Mass APH

Mix and TO-15 Mix

at no extra cost!

A. 

Higher Concentration =
MORE STANDARD for 
your money!

bromochloromethane
1-bromo-4-fluorobenzene 

(4-bromofluorobenzene)

chlorobenzene-d5
1,4-difluorobenzene

TO-14A Internal Standard/Tuning Mix

1ppm in nitrogen, 104 liters @ 1,800psi

cat. # 34408 (ea.)  

100ppb in nitrogen, 104 liters @ 1,800psi

cat. # 34425 (ea.)  

1ppm in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34408-PI (ea.)  

100ppb in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34425-PI (ea.)  

Environmental Air Monitoring Gas Standards

acetone
allyl chloride
benzyl chloride*
bromodichloromethane
bromoform
1,3-butadiene
2-butanone (MEK)
carbon disulfide* 
cyclohexane
dibromochloromethane
trans-1,2-dichloroethene
1,4-dioxane
ethyl acetate

4-ethyltoluene
heptane
hexane
2-hexanone (MBK)
4-methyl-2-pentanone
methyl 

tert-butyl ether (MTBE)

2-propanol
propylene
tetrahydrofuran
2,2,4-trimethylpentane
vinyl acetate
vinyl bromide

*Stability of this compound cannot be guaranteed.

TO-15 Subset 25 Component Mix (25 components)

1ppm in nitrogen, 104 liters @ 1,800psi

cat. # 34434 (ea.)  

100ppb in nitrogen, 104 liters @ 1,800psi

cat. # 34435 (ea.)  

1ppm in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34434-PI (ea.)  

100ppb in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34435-PI (ea.)  

benzene
1,3-butadiene
butylcyclohexane
cyclohexane
n-decane
2,3-dimethylheptane
2,3-dimethylpentane
n-dodecane
ethylbenzene
n-heptane
n-hexane
isopentane
isopropylbenzene

p-isopropyltoluene
methyl 

tert-butyl ether

1-methyl-3-ethylbenzene
naphthalene
n-nonane
n-octane
toluene
1,2,3-trimethylbenzene
1,3,5-trimethylbenzene
n-undecane
o-xylene
m/p-xylene (combined)

Massachusetts APH Mix (26 components)

1ppm in nitrogen, 104 liters @ 1,800psi

cat. # 34540 (ea.)  

1ppm in nitrogen, 21 liters @ 350psig (Pi-marked Cylinder)

cat. # 34540-PI (ea.)  

acetone
acrolein
benzene
benzyl chloride*
bromodichloromethane
bromoform
bromomethane
1,3-butadiene
2-butanone (MEK)
carbon disulfide*
carbon tetrachloride
chlorobenzene
chloroethane
chloroform
chloromethane
cyclohexane
dibromochloromethane
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
1,1-dichloroethane
1,2-dichloroethane
1,1-dichloroethene
cis-1,2-dichloroethene
trans-1,2-dichloroethene

1,2-dichloropropane
cis-1,3-dichloropropene
trans-1,3-dichloropropene
1,4-dioxane
ethanol*
ethyl acetate
ethyl benzene
ethylene dibromide 

(1,2-dibromoethane)

4-ethyltoluene
trichlorofluoromethane 

(Freon 11)

dichlorodifluoromethane 

(Freon 12 )

1,1,2-trichloro-

1,2,2-trifluoroethane 
(Freon 113)

1,2-dichlorotetra-

fluoroethane 
(Freon 114)

heptane
hexachloro-1,3-butadiene
hexane
2-hexanone (MBK)

4-methyl-2-pentanone 

(MIBK)

methylene chloride
methyl 

tert-butyl ether 

(MTBE)

methyl methacrylate
naphthalene
2-propanol
propylene
styrene
1,1,2,2-tetrachloroethane
tetrachloroethene
tetrahydrofuran
toluene
1,2,4-trichlorobenzene
1,1,1-trichloroethane
1,1,2-trichloroethane
trichloroethene
1,2,4-trimethylbenzene
1,3,5-trimethylbenzene
vinyl acetate
vinyl chloride
m-xylene
o-xylene
p-xylene

*Stability of this compound cannot be guaranteed.

TO-15 65 Component Mix (65 components)

1ppm in nitrogen, 104 liters @ 1,800psi

cat. # 34436 (ea.)  

100ppb in nitrogen, 104 liters @ 1,800psi

cat. # 34437 (ea.)  

1ppm in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34436-PI (ea.)  

100ppb in nitrogen, 110 liters @ 1,800psi (Pi-marked Cylinder)

cat. # 34437-PI (ea.)  

Choose the Appropriate Device for Your Sampling Needs

Canister

Gas 

Sampling Bag

Solvent 

Desorption Tube

Media Type

whole air

whole air

adsorption

Sensitivity

m

p

p

m

p

p

b

p

p

Technique

e

v

it

c

a

e

v

it

c

a

)

p

m

u

p

o

n

( 

e

v

i

s

s

a

p

Sample Type

d

e

t

a

r

g

e

t

n

i

b

a

r

g

d

e

t

a

r

g

e

t

n

i 

r

o

b

a

r

g

Analyte

wide range of VOCs

wide range of VOCs

sorbent specific

& permanent gases

Applications

ambient, IAQ,

ambient, IAQ

IAQ, IH

emergency response, IH

emission

Durability

reusable

one time use

one time use

Inertness

ri

a

f

ri

a

f

t

n

e

ll

e

c

x

e

Stability

e

t

y

l

a

n

a

y

b

s

e

ir

a

v

s

r

h

8

4

y

a

d

0

3

Sample Volume

0.4–6 L

0.5–100 L

varies by analyte

Sampling Time

minutes to days

minutes to hours

minutes to hours

U.S. • 110 Benner Circle • Bellefonte, PA 16823 • 1-814-353-1300 • 1-800-356-1688 • fax: 1-814-353-1309 • www.restek.com

China • phone: +86-10-5629-6620 • fax: +86-10-5814-3980 • cn.restek.com

France • phone: +33 (0)1 60 78 32 10 • fax: +33 (0)1 60 78 70 90 • www.restek.fr

Germany • phone: +49 (0)6172 2797 0 • fax: +49 (0)6172 2797 77 • www.restekgmbh.de

Italy • phone: +39-02-7610037 • fax: +39-02-70100100 • www.superchrom.it

Japan • phone: +81 (3)6459 0025 • fax: +81 (3)6459 0025 • e-mail: [email protected]

UK • phone: +44 (0)1494 563377 • fax: +44 (0)1494 564990 • www.thamesrestek.co.uk

Lit. Cat.# EVTG1073A 

© 2010 Restek Corporation. All rights reserved.

Printed in the U.S.A.

PATENTS & TRADEMARKS
Restek® patents and trademarks are the property of Restek Corporation. (See www.restek.com/Patents-Trademarks for full list.) Other trademarks appearing in Restek® literature or on 
its website are the property of their respective owners. The Restek® registered trademarks used here are registered in the United States and may also be registered in other countries.