The classroom doors of training institutions must have observation windows. From the relevant public information, the observation window on the classroom door of training institutions is mainly for safety reasons. The observation window on the classroom door allows teachers to observe the situation outside the door during teaching, such as whether there are strangers or other unsafe factors. The observation window also allows teachers or managers to quickly judge whether there are dangerous situations in the classroom when necessary, such as fire, earthquake and other emergencies, and can take escape or emergency measures in time to ensure the safety of students.