Public Lab Research note

What is EPA Method TO-15?

by kgradow1 | August 01, 2020 12:48 01 Aug 12:48 | #24242 | #24242


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.

Testing Methodology

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.

Compound CAS No.
Acetaldehyde (ethanal); C2H4O 75-07-0
Acetonitrile (cyanomethane); C2H3N 75-05-8
Acetophenone; C8H8O 98-86-2
Acrolein (2-propenal); C3H4O 0107-02-08
Acrylamide; C3H5NO 79-06-1
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
Benzene; C6H6 71-43-2
Benzyl chloride (a-chlorotoluene); C7H7Cl 100-44-7
Beta-Propiolactone; C3H4O2 57-57-8
Bis(2-Chloroethyl)ether; C4H8Cl2O 111-44-4
Bis(chloromethyl) ether; C2H4Cl2O 542-88-1
Bromoform (tribromomethane); CHBr3 75-25-2
1,3-Butadiene; C4H6 106-99-0
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.

Click here to learn more about EPA Method TO-15. Click here to learn more about EPA Method TO-14a. Click here to learn more about EPA Method TO-15a..

References and Further Reading

Stahl, H. (2019). What does Method TO-15 really mean?. Website. Retrieved from Jason S. Herrington. (2020). The new U.S. EPA Method TO-15A blog series - Part 1: It has arrived!!. Website. Retrieved from EPA. (2015). EPA Method TO-14a and TO-15: What's the difference?
Website. Retrieved from EPA Hazardous Waste Support Section SOP NO. HW-31, Revision 6. Analysis of Volatile Organic Compounds in Air Contained in Canisters by Method T0-15

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