EPA Method TO-15 is the procedure used to analyze air samples collected through canister sampling. “TO” stands for “toxic organics.” It is used to measure up to 97 volatile organic compounds (VOCs) of the total 189 hazardous air pollutants listed in the Clean Air Act. It is used for testing grab samples of ambient air.
TO-15 samples are analyzed using gas-chromatography / mass spectrometry. Gas chromatography is used to separate VOCs; mass spectrometry is used to measure. TO-15 samples are collected in summa canisters. This method is also used to test bucket samples in Tedlar bags.
Searchable List of Pollutants
This is a partial list. Click here for a full list of pollutants listed under this method.
|Acetaldehyde (ethanal); C2H4O||75-07-0|
|Acetonitrile (cyanomethane); C2H3N||75-05-8|
|Acrolein (2-propenal); C3H4O||0107-02-08|
|Acrylic acid; C3H4O2||79-10-7|
|Acrylonitrile (2-propenenitrile); C3H3N||107-13-1|
|Allyl chloride (3-chloropropene); C3H5Cl||0107-05-01|
|Aniline (aminobenzene); C6H7N||62-53-3|
|Benzyl chloride (a-chlorotoluene); C7H7Cl||100-44-7|
|Bis(chloromethyl) ether; C2H4Cl2O||542-88-1|
|Bromoform (tribromomethane); CHBr3||75-25-2|
|Carbon disulfide; CS2||75-15-0|
Does every lab test for these pollutants?
No. Because the machines need to be recalibrated for every chemical, labs will often only test a subset of chemicals. For instance, here is an example of a TO-15 list from Columbia Analytic Services (in California, testing 75 chemicals) compared to Environmental Analytic Services (also in California, testing 80 chemicals). It’s important to ask which chemicals they test for before you send your sample; if you’re not sure whether it’s on the list, you can also request that it be tested.
TO-15 v. TO-14a
Method TO-14a uses gas chromatography (GC) combined with a range of other tools. TO-15 is gas-chromatography / mass spectrometry only (GC-MS) and includes analysis of polar compounds due to better water management. Method TO-15 includes most (all?) chemicals listed in Method TO-14a. See this 2015 EPA memorandum outlining the differences.
TO-15 v. TO-15a
TO-15 was updated in 2016; there is also an updated method TO-15a, which was updated in September 2019. TO-15A which requires individualized cleaning certification for summa canisters and will likely exclude Tedlar bag sampling when it is finally rolled out; however, it is likely that many environmental testing labs will continue to offer both methods.
References and Further Reading
Stahl, H. (2019). What does Method TO-15 really mean?. Website. Retrieved from https://www.coxcolvin.com/what-does-method-to-15-really-mean/.
Jason S. Herrington. (2020). The new U.S. EPA Method TO-15A blog series - Part 1: It has arrived!!. Website. Retrieved from https://blog.restek.com/
EPA. (2015). EPA Method TO-14a and TO-15: What's the difference?
Website. Retrieved from https://www.epa.gov/sites/production/files/2015-06/documents/to14_15.pdf
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