large suppliers do not always include them even if the information is obtainable from retailers but written or telephone requests for paper copies will usually be responded to favourably. United Nations The United Nations (UN) defines certain details used in SDSs such as the UN numbers used to identify some hazardous materials in a standard form while in international transit. United States In the U.S., the Occupational Safety and Health Administration requires that SDSs be readily available to all employees for potentially harmful substances handled in the workplace under the Hazard Communication regulation. The SDS 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. Reviews of material safety data sheets by the U.S. Chemical Safety and Hazard Investigation Board have detected dangerous deficiencies. The board's Combustible Dust Hazard Study analyzed 140 data sheets of substances capable of producing combustible dusts. None of the SDSs contained all the information the board said was needed to work with the material safely, and 41 percent failed to even mention that the substance was combustible. As part of its study of an explosion and fire that destroyed the Barton Solvents facility in Valley Center, Kansas, in 2007, the safety board reviewed 62 material safety data sheets for commonly used nonconductive flammable liquids. As in the combustible dust study, the board found all the data sheets inadequate. In 2012, the US adopted the 16 section Safety Data Sheet to replace Material Safety Data Sheets. This became effective on 1 December 2013. These new Safety Data Sheets comply with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). By 1 June 2015, employers were required to have their workplace labeling and hazard communication programs updated as necessary – including all MSDSs replaced with SDS-formatted documents. SDS authoring Many companies offer the service of collecting, or writing and revising, data sheets to ensure they are up to date and available for their subscribers or users. Some jurisdictions impose an explicit duty of care that each SDS be regularly updated, usually every three to five years. However, when new information becomes available, the SDS must be revised without delay.