15 days. According to the query of coal mine safety net, special personnel must go to the professional department for training and hold relevant certificates after passing the examination by the professional department. All personnel on duty must undergo 15 days of pre-job training, and they can only take up their posts after passing the examination. So it takes 15 days to train gas workers. The training involves three types of work: coal mine gas inspection, coal mine gas drainage and coal mine drainage. Arrange courses reasonably according to post characteristics, training content and students' knowledge level.