This action revises EPA's definition of volatile organic compounds (VOC) for purposes of Federal regulations related to attaining the National Ambient Air Quality Standards (NAAQS) for ozone under title I of the Clean Air Act (CAA). This revision modifies the definition of VOC to say that t-butyl acetate (also known as tertiary butyl acetate or informally as TBAC or TBAc) will not be VOC for purposes of VOC emissions limitations or VOC content requirements, but will continue to be VOC for purposes of all recordkeeping, emissions reporting, and inventory requirements which apply to VOC. This revision is made on the basis that this compound has negligible contribution to tropospheric ozone formation. As a result, if you are subject to certain Federal regulations limiting emissions of VOCs, your emissions of TBAC may not be regulated for some purposes.