Air Testing FAQs

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Frequently Asked Questions (FAQs)

Q. When is it appropriate to request air testing canisters to be filled with helium?
Q. Are µg/m3 equivalent to parts per billion (ppbv)? Why or why not?
Q. Unit conversions – How do I convert µg/m3 to ppbv? How do I convert ppbv to µg/m3?
Q. What are TICs? How are they useful?
Q. Can you sample for sulfur compounds using a summa canister? Why or why not?
Q. What factors determine whether to use a canister or a Tedlar bag?
Q. How do you determine whether to take a whole-air sample or collect the sample on a solid sorbent?
Q. Can I sample for semi-volatile compounds out of a canister or Tedlar bag? Why or why not?
Q. Why do the MRLs change between each sample?
Q. How do you fill out the Chain of Custody (CoC)?
Q. How long is the holding time for canisters?
Q. What are the holding times for TO-14A/TO-15?
Q. What is the holding time for ASTM D5504?
Q. Do the media or samples need to be shipped cold?
Q. What are the dimensions of a summa canister?
Q. How much does a canister weigh?
Q. How do we ship the samples to you? Are there special shipping provisions?
Q: What is the difference between EPA TO-14, TO-14A, and TO-15?


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Q. When is it appropriate to request air testing canisters to be filled with helium?

A. Canisters may be backfilled with helium (prior to sampling) if you are sampling landfill gas that is expected to have high hydrogen sulfide and/or methane levels. The dilution of the sample will potentially bring concentrations of H2S/CH4 under the levels deemed hazardous by DOT.

Backfilling is only performed upon request from the client.

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Q. Are µg/m3 equivalent to parts per billion (ppbv)? Why or why not?

A. Unlike units for soil and water concentrations, µg/m3 are not equivalent to parts per billion in air; µg/m3 is a weight-to-volume ratio, while parts per billion in air is a volume-to-volume ratio.

Soil Water Air
µg/kg = ppb µg/L ≈ ppb µg/m3 ≠ ppb
w/w = w/w w/v ≈ w/v w/v ≠ v/v

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Q. Unit conversions – How do I convert µg/m3 to ppbv?

A. µg/ m3 * 24.46 / molecular weight of compound = ppbv
Example:
Carbon Tetrachloride Molecular Weight = 154
1.0 µg/m3 * 24.46 / 154 = 0.16 ppbV
5.0 µg/m3 * 24.46 / 154 = 0.79 ppbV

 

How do I convert ppbv to µg/m3?

(ppbV * molecular weight of compound) / * 24.46 = µg/m3
Example:
Benzene Molecular Weight = 78
1 ppbV * 78 / 24.46 = 3.2 µg/m3
5 ppbV * 78 / 24.46 = 16.0 µg/m3

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Q. Can you sample for sulfur compounds using a summa canister? Why or why not?

A. Yes and no. Using a traditional SS electropolished Summa canister, many sulfur compounds CAN be detected, such as carbon disulfide and dimethyl sulfide. However, a Summa canister is NOT suitable for hydrogen sulfide and mercaptans. Likely due to the direct H-S bonds in these compounds, they are highly reactive with the otherwise inert surface of the canisters and other metallic surfaces. When such samples are analyzed, the detected concentrations are much lower than the true concentrations of the sulfur compounds in the original sample.

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Q. What factors determine whether to use a canister or a Tedlar bag?

 

Parameter Canisters Bags
Concentration Range ppt - ppm ppm -- %
Applications Most Not suited for indoor or ambient air
VOC's Up to 250 C BP Much lower
Reduced Sulfur Not suitable for H2S, mercaptans 24 hour max holding time
Holding Times  30 Days 24-72 hours
Artifacts Minimal N, N-dimethylacetamide, phenol, COS, CS2

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Q. How do you determine whether to take a whole-air sample or collect the sample on a solid sorbent?

Parameter Whole-Air Soil Sorbent
Media Canister, bag Filters, traps, tubes (treated)
Compound VOC, sulfur HCHO, high boiling point VOCs, isocyanates, SVOCs
VOC analysis Cryogenic Thermal desorption Solvent desorption
Reporting limits ppb - ppt ppb – ppt ppm

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Q. Can I sample for semi-volatile compounds out of a canister or Tedlar bag? Why or why not?

A. Semi-volatile compounds should not be sampled from canisters or Tedlar bags.

Semi-volatile compounds are carried through the air column via particulates because of their non-volatile nature. Once inside a canister or bag, the particulate matter, and therefore the compounds, may adhere to the walls, substantially lowering the recovery or preventing any recovery at all.

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Q. Why do the MRLs change between each sample?

A. Method Reporting Limits (MRLs) can vary due to several reasons. It will depend on how much makeup gas must be added to the canister to achieve the proper pressurization required for analysis. If the canister still has significant vacuum when it arrives at the lab, a larger aliquot will be necessary, which will result in a larger dilution factor and higher MRLs. That is one reason why, when using a flow controller, it is important to sample for the time period for which the flow controller was specifically calibrated.

MRLs will also be higher if a smaller sample volume than prescribed must be analyzed. This occurs when a sample has high levels of contaminants. A dilution must be made to keep the results within the dynamic range of the instrument and to prevent contamination of the delicate instrumentation.

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Q. How do you fill out the Chain of Custody (CoC)?

A. Key fields: (view sample)

  • Client/address: This field is used to specify where the laboratory analytical report will be sent when completed. Fill in the name of your company and the complete address.
  • Phone number / fax number / email address: Helps us communicate with you if there are any questions and allows quick delivery of analytical results via fax or email. If an email address is provided, we will send your preliminary results to that address by default, unless otherwise specified.
  • Contact: The person at your company who should receive the completed analytical report from the laboratory. This may or may not be the same contact person as the Sampler.
  • Sampler: The actual person who performed the sampling.
  • Project Name and Project Number: Client specified. Provides additional information to the laboratory if available.
  • P.O. / Billing information: Please provide this information when available. It greatly facilitates the invoicing process for us and for you.
  • Project No.: Please leave this field BLANK. The lab will assign this number.
  • Client Sample ID: How the client identifies the samples. Can be any information or means of identifying the sample: alphanumeric combinations or actual descriptions.
  • Lab Sample No.: Laboratory specified. Please leave this field BLANK. The laboratory will create an in-house sample identification number.
  • Type of Sample: Specify the media type, such as canister or Tedlar bag.
  • Container ID (Serial #) and Flow Controller (Serial #): For Summa canisters and flow controllers. Please refer to the bar code and fill in the number. The bar code is generally prefixed with either an SC for Summa canisters or FC for flow controllers. The bar code label is black and white and should not be confused with the asset tag, which is silver and blue.
  • Sample volume: For use with solid sorbents only. Specifies the volume of air/sample pulled across the media. This value is usually in liters and is used for calculation purposes.
  • Analysis: Please specify which methods you are requesting and the turn around time (TAT) required. Standard TAT is 10 business days. Surcharges may be applied for expedited delivery of results and reports.
  • Comments: In the final column, please list any comments regarding the sampling process or the samples themselves that may be of use to the lab. This would include comments such as preservatives used (RSK 175 methods), extreme temperatures applied, odors observed, etc.
  • Additional Comments: Allows for any other comments the client would like to make, such as regarding TAT.

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Q. How long is the holding time for canisters?
A. Canisters do not have a specified holding time. EPA Method TO-15 has a suggested guideline of 30 days.

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Q. What are the holding times for TO-14A/TO-15?
A. EPA Method TO-15 has a suggested guideline of 30 days. However, the standard turnaround time (TAT) for sample analysis by an ALS Environmental Air Quality Laboratory is ten business days from the date of the sample receipt by the lab.

Samples taken in Tedlar bags must be analyzed within three days of sampling. This is to ensure that sample integrity is maintained.

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Q. What is the holding time for ASTM D5504?
A. According to ASTM D5504, samples collected in Tedlar bags must be tested within 24 hours of sampling. The 24-hour hold time is also specified in SCAQMD 1150.1 (for California requirements—South Coast Air Quality Management District) for sulfur testing.

Sulfur-containing compounds may also be collected in specially prepared canisters that are lined with a glass-like substance (such as Silco© canisters). While manufacturers of such canisters may list extended hold times, it is our goal to analyze these samples within 24 hours of sampling.

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Q. Do the media or samples need to be shipped cold?
A. Summa canister and Tedlar bag samples do not need to be sent cold.

What media or samples do need to be shipped cold?

  • Liquid samples for RSK-175 or for sulfur analysis
  • The impinger solution for anlalysis by TO-5A or TO-8A
  • DNPH silica gel tubes for analysis by TO-11A
  • PUF/XAD-2 cartridges for analysis by TO-13A
  • Sorbent tubes for analysis by TO-17
  • Liquid samples for 8315

“Cold” means shipped with something like Blue Ice to keep it around 4°C. DO NOT SHIP WITH REGULAR ICE! The ice can leak, allowing water to contaminate the samples and alter the results.

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Q. What are the dimensions of a summa canister?
A. Technical specifications for a 6L canister (courtesy of Meriter)
Size: ~12.38 H x 9.00" W
Weight: 5-6 pounds (~2.5 kg)
Volume: six liters nominal
Sample line connection: 1/4" tube fitting (Swagelok® type)
Pressure Rating: 41 psa maximum operating pressure
Temperature rating: -40°F to 400°F
Canister body: Stainless steel
All valves specified leak tight to 4 x 10-9 scc/sec He

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Q. How much does a canister weigh?
A. 5-6 pounds (~2.5 kg)

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Q. How do we ship the samples to you? Are there special shipping provisions?
A. In most cases, canisters can be shipped back to the air quality laboratory in the same boxes in which they were sent to you. Simply put the canisters back in the box, seal it, and send it back via Fed Ex.

Tedlar bags do not generally require special shipping. They can be sent in any cardboard box. Keep in mind, Tedlar bags should not be filled more than 1/2 to 2/3 full.

Cases that require special shipping: Natural gas, pure landfill gas, anything flammable or toxic. In such instances, we highly recommend speaking with a carrier such as UPS or Fed Ex for specific instructions. It will save you time and money! UPS has an excellent section on hazardous material shipping at their website and FedEx Dangerous Goods is also a very good resource.

View our instructions for Shipping Flammable Gas Samples (PDF)...

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Q: What is the difference between EPA TO-14, TO-14A, and TO-15?

A: EPA method TO-14 was originally published in March 1989 in the Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. In January 1999, EPA TO-14 was revised and updated as TO-14A in the Second Edition of the Compendium of Methods; as such, EPA TO-14 has been superseded by TO-14A. TO-15 was a new method added to the Second Edition of the Compendium in January 1999. TO-15 is larger in scope and better defined for the analysis of VOCs in air and other gaseous matrices than TO-14A. In practice, TO-15 has supplanted TO-14A as the preferred method for the analysis of VOCs in air. Unless otherwise specified by project documentation, permit requirements or other regulation, TO-15 is the method recommended by ALS Environmental.

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