Four hours. According to the Law of People's Republic of China (PRC) on the Prevention and Control of Occupational Diseases, it can be known that the company should provide training on the prevention and control of occupational hazards for coal mine workers before and during their posts. The pre-job training time is not less than 4 hours, and the on-the-job training time is not less than 2 hours per year. Workers who have not been trained in the prevention and control of occupational hazards are not allowed to work in the well. Those who fail the exam must pass the make-up exam before entering the well.