One year. According to the inquiry of catering service management system, catering service units should conduct food safety training and assessment for employees at least once a year. Specific catering service providers shall conduct food safety training and assessment for their employees at least once every six months. The contents of the training and assessment are the knowledge of laws and regulations, the basic knowledge of catering food safety, and the food safety management system, processing and production process, food safety management skills and food safety accident emergency disposal knowledge of the unit.