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The PPM Blog

A Quick Overview of EPA Tanks 5.0 Beta Version

a man wearing a suit and tie smiling at the cameraContributed by Jamie Godbold, Senior Project Manager, PPM Consultants

In case you missed it, the EPA has proposed a few updates to Chapter 7 (Liquid Storage Tanks) of its Compilation of Air Emissions Factors from Stationary Sources (commonly referred to as AP-42). While that may not be too exciting to most of you, you might be a little more interested to hear that the EPA is also working on TANKS version 5.0. That’s right…it seems that the EPA will offer an updated version of TANKS for public use…and for free!

Historically, TANKS was developed by contractors for the EPA, who then made it publicly available for use. This simplified the complicated effort of applying the emission calculation methodologies provided in Chapter 7. This also ensured that emissions from storage tanks were quantified consistently. Over the years, though, the calculation methodologies in AP-42 evolved, while the TANKS program lagged behind. The last version (TANKS 4.09d) was made available for use in 2006 and contained a variety of flaws that were problematic for users and concerning for regulatory agencies. These flaws provided opportunities to unintentionally estimate emissions that weren’t always correct. Users had to be pretty knowledgeable about the program’s limitations and take steps to ensure that the program produced results that were consistent with AP-42 methodologies and were conservative for permitting purposes. Because of these challenges, regulatory agencies, including the EPA, determined that the TANKS 4.09d program was not reliably functional and no longer offered any assistance to users. The EPA punted to industry and permittees to developed tools to replace TANKS. If you’re still reading this, you probably know that those tools are expensive and often present their own challenges to users.

Enter TANKS 5.0. TANKS 5.0 was developed by the American Petroleum Institute (API) to correct the errors known to exist within version 4.09d and is currently being beta tested by the public and EPA. While previous versions required a program download, TANKS 5.0 is accessed through the internet via your web browser and can currently be found at . The EPA is accepting comments on TANKS 5.0 as well as to the proposed changes to AP-42 Chapter 7 through the end of April 2024.

Here’s a quick summary of what I noticed in TANKS 5.0, based on my trial run of the beta-test version:

  1. The web-based interface is pretty intuitive and user-friendly with data entered via a series of drop-downs.
  2. There is a 37-page User Guide, but it doesn’t provide much practical or useful guidance. Be prepared to refer to AP-42 and historical TANKS documents to solve your questions.
  3. Users can utilize TANKS 5.0 to calculate working & breathing losses (referred to as Routine Losses) as well as roof landings or tank cleanings (referred to as Emission Events).
  4. Results from Routine Losses are presented as a spreadsheet which can be downloaded for use; however, the results do not summarize or include the inputs used which makes QA/QC difficult at best.
  5. In the Routine Losses report I built, I didn’t see an option to speciate emissions from hazardous air pollutants (HAPs). Results provided emissions as total VOCs only.
  6. The inputs are saved within your browser data but can also be exported into an excel file; however, the data is not in a form that is easily read or understood.
  7. Results from Emission Events are presented only as text on the web page. There is no excel file to download or report provided for documentation purposes.
  8. Not all scenarios or equations are included within TANKS 5.0 which may perhaps make it difficult to convert your current methodologies into a form that is compatible with TANKS 5.0.

The changes proposed by EPA to AP-42 Chapter 7 are fairly innocuous. Many of the changes are provided for clarification or to update format. One change worth noting is that equations and related language were added for use in estimating emissions from square or rectangular tanks. It is perhaps worth noting that the proposed text includes language that reads, “The emission estimation procedures outlined in this chapter have been used as the basis for the development of a software program to estimate emissions from storage tanks. The software program entitled ‘TANKS’ is available through the U. S. Environmental Protection Agency website. While this software does not address all of the scenarios described in this chapter, known errors have been corrected and a new version, TANKS 5.0, is now available.” AP-42 continues to caution against use of commercially available storage tank emissions estimation software programs without understanding the risks and agreement with AP-42 Chapter 7, since these programs have not been reviewed or approved by the EPA.

To sum things up, it appears that the EPA will again offer a free, EPA-approved version of TANKS which may become available for use upon issuance of an updated AP-42 Chapter 7. While the new TANKS version 5.0 does address the errors known to exist in the previous version, it still has shortcomings (most notably the report format and lack of detail), which will likely be very unappealing to regulatory agencies as well as permittees. After all, what good is a result if you can’t document or easily explain how you developed those results. Kudos to EPA and API for the effort and work thus far. Hopefully the final TANKS 5.0 version will be something everyone will accept and utilize.

PPM Consultants specializes in air permitting and compliance support to all industry types. For more information or assistance regarding tank emission calculations or our ability to provide environmental support, please contact me at

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