Mobile Site Full Version
share:

Frequently Asked Questions: Air Sampling

  1. What is the maximum temperature for Restek TO-Can and SilcoCan canisters?
  2. What is the maximum pressure for Restek TO-Can and SilcoCan canisters?
  3. What is the difference between a TO-Can and a SilcoCan canister?
  4. Are Restek air sampling canisters shipped under pressure or vacuum?
  5. Can Restek repair canisters and controllers?
  6. What critical orifice should I select based on my canister size and sampling time requirements?
  7. How can I optimize my TO-14 or TO-15 analysis?
  8. Does Restek provide gas calibration standards?
  9. What do I do with my empty reusable gas cylinders?
  10. Can my gas standard be recertified?
  11. What regulator should I use with my gas standard?
  12. How can I troubleshoot pressure problems in my gas standard?
  13. What is the maximum pressure for gas sampling bags?
  14. Which bag should I use for my sample?
  15. How long can I keep my samples in gas sampling bags?
  16. When should I use solvent desorption (thermal desorption) vs. other air sampling techniques?
  17. What is the advantage of using Siltek-treated gas sample loops or valves?
  18. What kind of fittings are on Restek’s gas sample loops?
  19. What is a “PI” marked or TPED gas sample cylinder?
  20. What is the difference between treated and untreated cylinders?
  21. How do I order a dip tube for my sample cylinder?
  22. How can I clean a treated gas sampling cylinder?
  23. How do you convert a gas standard concentration from percent to ppmv?

If your question doesn’t appear on the list, you can contact Restek’s expert chemists.

  1. What is the maximum temperature for Restek TO-Can and SilcoCan canisters?

  2. The maximum recommended temperatures are as follows:

    • 80 °C for a SilcoCan canister (with or without a gauge) cleaned in the presence of oxygen.
    • 120 °C for a TO-Can or SilcoCan canister with a gauge cleaned in the presence of an inert gas.
    • 140 °C for a TO-Can or SilcoCan canister without a gauge cleaned in the presence of an inert gas.

    Do not exceed the maximum recommended temperatures.

    Back to top of page


  3. What is the maximum pressure for Restek TO-Can and SilcoCan canisters?

  4. The maximum recommended pressure for all Restek air sampling canisters is 40 psi (~ 2.75 bar) as described in these instructions. Do not exceed the maximum recommended pressure.

    Back to top of page


  5. What is the difference between a TO-Can and a SilcoCan canister?

  6. Restek’s TO-Can canisters (toxic organics) are general-purpose canisters that are intended to be used for methods such as TO-14A, TO-15, IP-1A, ASTM D5466, OSHA PV 2120, and NJ DEP Low Level TO-15. These canisters feature a proprietary electropolished surface that is designed to maintain compound stability. TO-Can canisters are functional equivalents to “SUMMA” canisters.

    SilcoCan canisters are Siltek treated and are more inert than TO-Can canisters. They are ideal for low-level reactive sulfurs (5–20 ppb) as well as some of the more challenging TO-14A and TO-15 compounds. These Siltek-treated canisters are typically recommended for the collection and storage of sulfur-containing or brominated compounds. Siltek-treated accessories should be used with these canisters to provide the most inert sampling pathway.

    Back to top of page


  7. Are Restek air sampling canisters shipped under pressure or vacuum?

  8. Our air canisters are shipped under pressure (~15 psi [~1 bar]) of dry nitrogen; however, they can be shipped under vacuum (~30” Hg) upon request.

    Back to top of page


  9. Can Restek repair canisters and controllers?

  10. Repair services are available for most of our current canister and controller products. Custom catalog (cat.#) numbers and details for these repairs are presented in the table below.

    Equipment to Repair

    Order cat.#

    Service Includes

    Sampling kit / flow controller

    550131

    all new rubber seals in the flow controller and orifice, as well as frit replacement

    Restek canisters with RAVE valves

    569419

    valve replacement, leak testing, and cleaning

    Restek canisters with Parker valves

    560838

    valve replacement, leak testing, and cleaning

    Restek canisters with Swagelok valves

    563801

    valve replacement, leak testing, and cleaning


    Reconditioning services are also available for our current generation canisters. We will replace the valve and clean and leak test the canister at a cost that is less than replacing the entire canister. To request reconditioning services, please follow these steps:

    1. Contact Restek’s customer service team or your local international representative to place an order for custom cat.# 569419 (RAVE diaphragm valve) using a purchase order.

    2. Obtain a service authorization number (SRV#) to place on the shipping container.

    3. Clean the canister before shipment to Restek.

    4. Include a completed “Health and Safety Declaration.”

    5. Return the canister intact. Do not remove valves, gauges, or parts from the canister.

    To request any of these repair services, simply contact our Customer Service Team or your local Restek International Representative.

    Back to top of page


  11. What critical orifice should I select based on my canister size and sampling time requirements?

  12. The following table lists the recommended orifice diameters, associated flow rate ranges, and canister volumes and sampling times:

    Canister Volume/Sampling Time

     

    Orifice

    Siltek-Treated

    Stainless Steel

    400 cc

    1 Liter

    3 Liter

    6 Liter

    15 Liter

    Flow

    Size

    cat.#

    cat.#

    8 hour

    24 hour

    48 hour

    125 hour

    0.5–2 mL/min

    0.0008"

    24217

    24216

    2 hour

    4 hour

    12 hour

    24 hour

    60 hour

    2–4 mL/min

    0.0012"

    24160

    24165

    1 hour

    2 hour

    6 hour

    12 hour

    30 hour

    4–8 mL/min

    0.0016"

    24161

    24166

    1 hour

    4 hour

    8 hour

    20 hour

    8–15 mL/min

    0.0020"

    24162

    24167

    2 hour

    3 hour

    8 hour

    15–30 mL/min

    0.0030"

    24163

    24168

    1 hour

    1.5 hour

    4 hour

    30–80 mL/min

    0.0060"

    24164

    24169

    0.5 hour

    1 hour

    80–340 mL/min

    0.0090"

    22101

    22100

    Back to top of page


  13. How can I optimize my TO-14 or TO-15 analysis?

  14. In addition to our comprehensive Guide to Whole Air Canister Sampling, we have an in-depth series of blog posts detailing air analysis. These valuable resources will help you optimize your analyses.

    Back to top of page


  15. Does Restek provide gas calibration standards?

  16. Restek provides gas calibration standards manufactured by Spectra/Linde, Airgas (formerly Scott/Air Liquide), and other gas calibration suppliers. These air standards include TO-14A, TO-15, environmental blends, Scott transportable pure gases & mixtures, natural gas, and refinery gas, as well as related accessories. We can also source custom, made-to-order gas calibration standards. To request a quote, simply complete this form.

    Back to top of page


  17. What do I do with my empty reusable gas cylinders?

  18. Local regulations can vary greatly. If you wish to dispose of or recycle empty cylinders, be sure to do so according to local regulations. Some cylinders can be returned to the manufacturer; for more information, directly contact Spectra/Linde Gases, Inc. (1-800-932-0624) or Airgas (formerly Scott/Air Liquide gas) (1-800-331-4953).

    Back to top of page


  19. Can my gas standard be recertified?

  20. Recertification is available for gas standards. Gas standards can be expensive and tend to be stored in the lab for months, if not years, so it is wise to have the composition recertified by a qualified vendor. For gas standards purchased from Restek, request recertification directly from Spectra/Linde Gases, Inc. (1-800-932-0624) or Airgas (formerly Scott/Air Liquide gas) (1-800-331-4953). For gas standards purchased from vendors other than Restek, it is necessary to contact the vendor who manufactured the mixture.

    Back to top of page


  21. What regulator should I use with my gas standard?

  22. We offer six regulators for our gas standards. Specifications are summarized below:



    DCG Partnership Cylinders:

    Size: 7.6 x 24 cm

    CGA-170/110 connection

    U.S. DOT Specs: DOT-4B-240ET

    Please note: This cylinder is not approved for use in Canada.

    Recommended regulator:
    cat.# 22032



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

    Aluminum construction

    Size: 8.3 x 29.5 cm

    Volume/Pressure:
      110 liters of gas @ 1,800 psi

    CGA-180 outlet fitting

    Weight: 2.2 lb/1 kg

    DOT Specifications: 3AL2216

    Recommended regulator:
    cat.# 26371, 26372, 21572, or 21572-R100




    Spectra (Linde) 104 L:

    Aluminum construction

    Size: 8 x 24 cm

    Volume/Pressure:
      104 liters of gas @ 1,800 psi

    CGA-180 outlet fitting

    Weight: 1.5 lb/0.7 kg

    Recommended regulator:
    cat.# 21572, 21572-R100, 26371, or 26372




    Airgas 110 L:

    Aluminum construction

    Size: 8.3 x 29.5 cm

    Volume/Pressure:
      110 liters of gas @ 1,800 psi

    CGA-180 outlet fitting

    Weight: 2.2 lb/1 kg

    DOT Specifications: 3AL2216

    Recommended regulator:
    cat.# 26371, 26372, 21572, or 21572-R100




    Airgas 14 L:

    Contents: 14 liters

    Pressure: 240 psig (17 bar)

    Outlet Fitting: CGA 160

    Weight: 1.5 lb/0.7 kg

    Dimensions:
      3" diameter x 11" height
      (7.6 x 28 cm)

    DOT Specifications: 4B240

    Please note: This cylinder is not approved for use in Canada.

    Recommended regulator:
    cat.# 22690




    Airgas 48 L:

    Contents: 48 liters

    Pressure: 300 psig (21 bar)

    Outlet Fitting: CGA 165

    Weight: 1.75 lb/0.8 kg

    Dimensions:
       4" diameter x 16 ¼" height
       (10.2 x 41 cm)

    DOT Specifications: 39 NRC

    Please note: This cylinder is not approved for use in Canada.

    Recommended regulator:
    cat.# 22691



    Back to top of page


  23. How can I troubleshoot pressure problems in my gas standard?

  24. The most common problem encountered with gas standards is the absence of a pressure reading at the regulator. To check your regulator, remove it from the cylinder, and connect it to a cylinder that you are sure has pressure. If the regulator registers a reading on the “good” cylinder, the problem is likely that the cylinder in question is empty. If the regulator does not register a reading on the “good” cylinder, then the problem is the regulator and it must be repaired or replaced.

    Back to top of page


  25. What is the maximum pressure for gas sampling bags?

  26. The maximum recommended pressure for all Restek gas sampling bags (including Tedlar, ALTEF, and multi-layer foil bags) is approximately 2 psi (~ 0.14 bar) or ≤80% filled. Exceeding the pressure or fill volume may result in a leak and/or sample loss.

    Back to top of page


  27. Which bag should I use for my sample?

  28. ALTEF bags are an alternative to Tedlar bags for the collection of volatile organic compounds (VOCs); however, these bags are not recommended for ketones, acetates, hydrogen sulfide, and permanent gases.

    Multi-layer foil gas sampling bags are recommended for light, low molecular weight analytes including methane, carbon dioxide, carbon monoxide, and permanent gases. These bags are not recommended for low (ppm) level VOCs due to background levels.

    Tedlar bag compatibility is similar to ALTEF bag compatibility, except that Tedlar bags contain trace amounts (≤1%) of dimethylacetamide (DMAC) and phenol, due to their manufacturing process, while ALTEF bags do not. Therefore, some labs prefer ALTEF bags to prevent exposure of their samples to DMAC and phenol.

    For reactive compounds like ammonia and chlorine gas, Restek does not recommend the use of sampling bags. Instead, we recommend SilcoCan air sampling canisters.

    Back to top of page


  29. How long can I keep my samples in gas sampling bags?

  30. Single-use sample bags are typically intended for short-term storage (approximately 24–48 hours). Storage for >48 hours is usually not recommended, unless validation studies verify longer stability of target analytes. We recommend the following guidelines when using gas sampling bags:

    Before Sampling

    • Store unused bags in a clean environment, sealed in an outer bag to prevent adsorption of contaminants.
    • Preclean bags before use by flushing with high-purity nitrogen.
    • Leak rate should not exceed 0.1" Hg/min.

    During Sampling

    • Do not fill bags more than 80%.
    • Be sure the PTFE tubing used for bag connection is clean.
    • Use a vacuum box sampler for direct bag filling, in order to avoid contamination from a sampling pump.
    • 3 L/min is a typical flow rate.

    After Sampling

    • Bags are intended for a single use due to potential sample adsorption onto the bag film.
    • Hold times are typically 48 hours, unless validation study demonstrates longer stability.
    • Protect samples from direct sunlight and store above 0 °C to prevent condensation.
    • Transport in rigid, opaque container to prevent bag puncture; do not ship by air unless samples will be kept in a pressurized area.

    Back to top of page


  31. When should I use solvent desorption (thermal desorption) vs. other air sampling techniques?

  32. Please refer to the following table for a comparison of the advantages and disadvantages of canisters, gas sampling bags, and solvent desorption tubes (thermal desorption tubes).

     

    Canister

    Gas Sampling Bag

    Solvent/Thermal Desorption Tube

    Media Type

    whole air

    whole air

    adsorption

    Sensitivity

    ppt-ppb

    ppb-ppm

    ppb-ppm

    Technique

    passive (no pump)

    active

    active/passive

    Sample Type

    grab or integrated

    grab or integrated

    grab or integrated

    Analyte

    wide range of VOCs & permanent gases

    wide range of VOCs & permanent gases

    sorbent specific

    Applications

    ambient, IAQ, emergency response, IH

    ambient, IAQ, emission

    ambient, IAQ, IH

    Durability

    reusable

    one time use

    solvent: one time use; thermal: reusable (performance is solvent specific)

    Inertness

    excellent

    fair

    fair

    Stability

    30 day

    48 hrs

    varies by analyte

    Sample Volume

    0.4–15 L

    0.5–100 L

    varies by analyte

    Sampling Time

    seconds to days

    minutes to hours

    minutes to hours

    Back to top of page


  33. What is the advantage of using Siltek-treated gas sample loops or valves?

  34. Siltek treatment is a passivation process that applies an inert, integral layer to components used for chromatographic analysis. Unlike traditional deactivations, it is not susceptible to cleavage or formation of active silanols and, therefore, greatly reduces both bleed and the breakdown or adsorption of active components, compared to conventional surface coatings. This unique surface provides an inertness range that surpasses other surface deactivations used in gas chromatography. In sensitive analyses, Siltek-deactivated system components provide outstanding analytical results. For more information on Siltek treatment and treated products, refer to our surface treatment FAQs.

    Back to top of page


  35. What kind of fittings are on Restek’s gas sample loops?

  36. Our gas sample loops have 1/16" fittings, a 1 mm inner diameter (ID), and are for use with “W type” valves.

    Back to top of page


  37. What is a “-PI” marked or TPED gas sample cylinder?

  38. To comply with the European Union Transportation of Pressurized Equipment Directive (TPED), Restek offers “-PI” marked cylinders for use in European Union (EU) countries. The mathematical Pi mark is required to be stamped into the cylinder (metal) if the cylinder is sold into an EU country.

    Back to top of page


  39. What is the difference between treated and untreated cylinders?

  40. Siltek-treated sample cylinders are recommended for the collection, storage, and analysis of ppb levels of sulfur, mercury, or other sensitive compounds. Because these compounds quickly react with stainless steel surfaces, accurate determination of these compounds is not possible when samples are collected and stored in untreated sample cylinders. Siltek passivation techniques bond an inert layer into the surface of stainless steel, preventing active compounds from reacting with or adsorbing to the steel. Please refer to this stability study for additional information.

    Back to top of page


  41. How do I order a dip tube for my sample cylinder?

  42. A dip tube (also known as an outage tube) provides vapor space above liquefied gases in a sampling cylinder so that if expansion occurs with an increase in temperature, the pressure is not significantly increased. Basically, the length of the dip tube is used to determine the filling capacity of the cylinder.

    This blog post contains detailed instructions on how to select and order an appropriate dip tube. Restek sample cylinder valves can be ordered with or without a dip tube from this page or by contacting our U.S. customer service team at csreps@restek.com or your local Restek representative.

    Back to top of page


  43. How can I clean a treated gas sampling cylinder?

  44. To clean a treated part, rinse with a solvent that will dissolve probable surface contaminants (i.e., use a nonpolar solvent to remove hydrocarbon contaminants, or a more polar solvent to remove more active contaminants). Avoid using cleaners containing abrasives as they can scratch the surface layer. Mild sonication might assist in removing contaminants, but do not oversonicate—this could damage the surface layer. Do not use basic solutions with pH>8.

    Back to top of page


  45. How do you convert a gas standard concentration from percent to ppmv?

  46. For gas standard concentrations, percentage is equivalent to 10,000 ppmv. For example, a concentration of 8.5% is equal to 85,000 ppmv.

    Back to top of page