On May 13, 2010, the U.S. EPA issued the Greenhouse Gas (GHG) Tailoring Rule. This rule added the definition of "subject to regulation" which specifies when GHGs are considered for determining major source status under Title V Operating Permit programs. Beginning on July 1, 2011, the requirement to obtain a Title V operating permit is applied to sources based solely on their potential GHG emissions, even if they would not apply based on the emissions of any other pollutant. The GHG Tailoring Rule establishes a potential emissions threshold for Title V Operating Permit applicability of 100,000 tons per year of Carbon Dioxide Equivalent (CO2e), excluding biogenic sources of CO2. Therefore, existing sources that do not currently have a Title V Operating Permit and have potential emissions exceeding this threshold must obtain a Title V Operating Permit.

Per the GHG Tailoring Rule, Title V applications are required to be submitted no later than July 1, 2012. Alternatively, sources can accept a federally enforceable limit in a synthetic minor operating permit to ensure that the threshold will not be exceeded. If the source chooses to accept a federally enforceable limit on GHG emissions to remain below the threshold, the source must apply for and obtain a synthetic minor operating permit by July 1, 2012. Additional information on the Title V permitting of GHG emissions can be found on USEPA's website for Clean Air Act Permitting for GHGs.