Updates to the Hazardous Organic National Emission Standards for Hazardous Air Pollutants (HON) were finalized by the U.S. Environmental Protection Agency in May 2024 and took effect July 15, 2024. The rule updates federal air emissions requirements for chemical manufacturing facilities, tightening flare performance standards, expanding controls on ethylene oxide (EO) and other hazardous air pollutants, and establishing phased compliance timelines. Key requirements take effect in 2026 and 2027.