If the hazardous substance is produced in on-site processes such as incineration, it’s considered present at the facility and subject to Section 302 of the Emergency Planning and Community Right-to-Know Act reporting requirements if the amount on site exceeds the threshold planning quantity at one time.
If the release is federally permitted under Section 101(10) of the Comprehensive Environmental Response, Compensation, and Liability Act, including permitted emissions under the CAA, then the release doesn’t need to be reported under Section 304.