CFR › Title 40 › Part 439 › §439.2640 CFR §439.26Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗Copy linkExcept as provided in 40 CFR 403.7 and 403.13, any existing source subject to this subpart must achieve the following standards by September 21, 2001: