On October 15, 2015, EPA published a rule titled “National Emission Standards for Hazardous Air Pollutants for the Primary Aluminum Reduction Plants” (80 FR 62390) which set new emissions limits for particulate matter (PM) for anode bake furnaces, paste production plants and five subcategories of potlines. On July 9, 2019, EPA received a petition from Intalco Aluminum LLC requesting that EPA initiate a rulemaking to revise the PM emissions limits for one of the potline subcategories (i.e., side-worked prebake potlines). The petitioner claims that, while the rule requires the compliance demonstration for these PM emissions limits be based on test data that represent a complete operating cycle, the underlying data used by EPA to establish the emissions limits was not test data representative of a complete operating cycle. EPA is evaluating this issue and accompanying data provided by the petitioner. Based on an internal, preliminary review, EPA thinks the petition has merit. The agency intends to review the submitted data and, if appropriate, propose revised PM emissions limits for this potline subcategory.