On January 25, 2018, EPA announced it is withdrawing, the “Once In, Always In” (OIAI) policy under the Clean Air Act. New EPA guidance allows stationary sources of hazardous air pollutants (HAPs) that are classified as “major sources” to limit their HAP emissions to below major source thresholds and thereby be reclassified as “area” sources at any time. In the past, major sources of HAPs remained subject to major source requirements, even if they took steps to reduce their potential to emit, or PTE, below major source thresholds.
Area sources are subject to less onerous emission requirements than are major sources. The withdrawal of the OIAI Policy is effective immediately.