Both the United States and Canadian governments require that employers post certain safety posters in every workplace. Also, there are requirements to post labor law posters as well. These posting requirements are more complex than most think. The required posters not only vary based upon what country you are in, but they also are specific to the State (or Province) in which you operate. Below is a link that will help you comply with these posting regulations.
http://www.safetyawakenings.com/required-safety-labor-law-posters-osha/