The New U.S. EPA Method TO-15A blog series – Part 1: It has arrived!!!

March 2016, the U.S. EPA announced it would start updating the long overdue (i.e., not updated since 1999) Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air Second Edition (625/R-96/010b), by soliciting public comments and suggestions on Method TO-15*. May 2016, the agency closed the open comment period and set off to consolidate, decipher, and incorporate relevant improvements/modifications into a revised TO-15A.

August 2018, Dave Shelow (now retired) of the Office of Air quality Planning and Standard (OAQPS) provided an “Update on Method TO15A” at the National Ambient Air Monitoring Conference (NAAM). It was during this presentation that the agency pulled back the curtain just enough to give the public a sneak peak of the pending method modifications. After all, it had been 2 years since the last communication, so the air community was getting anxious. There were several “biggies;” however, the one to receive the most buzz within the air canister circles appears to have been the canister cleanliness criterion which was reduced from 0.2 ppbv at 30 psig to ≤0.020 ppbv (≤20 pptv) at 0 psig. No one jumped from any roof tops, as all of the discussed modifications were still pending an external peer review. However, it definitely created a stir and further built the anticipation as we all waited to see if the final TO-15A was going to indeed incorporate this drastic change; and what other doozies may be lurking, but not yet revealed.

After 4 years and much anticipation, the new U.S. EPA Method TO-15A was recently published to the agency’s Ambient Monitoring Technology Information Center (AMTIC) website. It is important to note, that I am not digging on the EPA with my 4 year comment, just stating a fact. As alluded to in 2018, section 10.2 (Verification of Canister Cleanliness Prior to Sample Collection) on page 38 confirms the new canister cleaning criterion is ≤ 20 pptv (0.02 ppbv) per target VOC when a canister is filled to standard ambient pressure (101.3 kPa absolute or 14.7 psia). Note that this is not just a 10x reduction (i.e., from 200 to 20 pptv), rather we are looking at a 30x reduction due to the requirement now stipulating at 0 psig instead of the previous 30 psig. The new method makes accommodations for continuing to fill your canister blanks to 30 psig (and other pressures); however, as shown below in Table 10-3 on page 39 of the method, you would now need to certify to <6.5 pptv.

So, where am I going with all this? Well, the new method clearly has a canister cleaning requirement, which I am confident will give a fair number of laboratories some angst. Therefore, this is the kick-off post for a series of posts focused on the new Method TO-15A. In particular, the next few posts will be centered around how one gets cleaner canisters and meets the necessary detection limits with their instrumentation. So stay tuned for the next post where we show you how to take your canister blanks from the following red trace down to the blue trace:

y-axis is the same for both traces, so no trickery.

*"Determination of Volatile Organic Compounds (VOCs) in Air Collected in Specially Prepared Canisters and Analyzed by Gas Chromatography/ Mass Spectrometry (GC/MS),"