The main purpose of the switch from the MSDS to the SDS is to create a simpler and more unified standard way to communicate the hazards of a chemical. Prior to the switch companies may have had MSDS in multiple formats with information on those formats in varied locations. By moving to a universal format it makes it easier for employees to find information on a chemical, it also lowers the burden for chemical manufactures. There is no requirement to keep old MSDS on file once you have obtained and SDS to replace it. However, employers may want to keep an electronic copy on file, especially if existing stocks of the chemical were purchased under the older MSDS.