A national emission standard for sulfur dioxide and reduced sulfur compounds was proposed under authority of section III of the Clean Air Act. The intent of the standard was to minimize reduced sulfur and sulfur dioxide emissions from refinery sulfur recovery plants to the level attainable with best available control technology. Twenty-one comment letters were received from the petroleum industry, State and local air pollution control agencies, and other federal agencies. As a result of these comments, changes have been made in the promulgated standard. The major change is an exemption from the standard for sulfur recovery plants of 20 long tons per day (LTD) or less associated with a small petroleum refinery.