Subject to certain exceptions, the Environmental Protection Agency (EPA) is approving State Implementation Plan (SIP) revisions submitted by the State of Colorado on May 14, 2018, May 8, 2019, May 13, 2020 and March 22, 2021. The revisions are to Colorado Air Quality Control Commission (Commission or AQCC) Regulation Number 7 (Reg. 7). The revisions to Reg.