EPA recently finalized a guidance document titled “Counting GHG Fugitive Emissions in Permitting Applicability” that addresses how sources should count fugitive GHG emissions when conducting NSR analyses under the GHG Tailoring Rule. EPA has clarified that “fugitive emissions accounting provisions for listed and non-listed source categories apply to the Tailoring Rule ‘subject to regulation’ thresholds for GHGs in the same manner as they do to the statutory and regulatory mass-based thresholds for any regulated NSR pollutant.” EPA prepared this guidance document in response to a question from industry regarding how fugitive GHG emissions should be counted when determining whether a new major source or major modification at an existing source will trigger the GHG permitting threshold in the Tailoring Rule.