This action revises EPA's definition of volatile organic compounds (VOC) for purposes of preparing State implementation plans (SIP's) to attain the national ambient air quality standards (NAAQS) for ozone under title I of the Clean Air Act (Act) and for the Federal implementation plan (FIP) for the Chicago ozone nonattainment area. This action adds HFC 43-10mee and HCFC 225ca and cb to the list of compounds excluded from the definition of VOC on the basis that these compounds have negligible contribution to tropospheric ozone formation. These compounds are solvents which could be used in electronics and precision cleaning.