So-called dry toilets, also known as dry toilets, are often seen on urban civil air defense basement drawings. Because civil air defense basements are used to hide people or objects in wartime to prepare for war, they have the function of isolating the outside world. , so the septic tank cannot be connected to the outside world. Since it is a closed place, the civil air defense toilet is also called (dry toilet) or (dry toilet), which refers to the temporary use of the toilet without using running water for flushing