In the U.S., the Occupational Safety and Health Administration requires that Material Safety Data Sheets (SDS/MSDS) be available to employees for potentially harmful substances handled in the workplace under the Hazard Communication regulation. The SDS/MSDS is also required to be made available to local fire departments and local and state emergency planning officials under Section 311 of the Emergency Planning and Community Right-to-Know Act. The American Chemical Society defines Chemical Abstracts Service Registry Numbers (CAS numbers) which provide a unique number for each chemical and are also used internationally in SDSs/MSDSs.