How often are the NEI data updated and how frequently are the data published?

The full NEI is created for every third inventory year (e.g., 2008, 2011, 2014, and 2017).  The data for each version has been updated two times each for the 2008, 2011, and 2014 NEI cycles.  For the 2017 NEI and beyond, the EPA is trying to publish only a single version, with draft versions being available to stakeholders such as state, local, and tribal air agencies for review in advance. Each time a new version is created, it is published soon after.  Typically, updates to an existing version occurs every year and a half.

In addition, the EPA collects from state, local, and tribal air agencies point source data for larger sources every year (see the Air Emissions Reporting Rule for specific emissions thresholds).  While these data are not typically published as a new NEI, they are available publicly upon request and are also included in EPA modeling platforms that are created for years other than the triennial NEI years.