The hotel room adopts fan coil unit+fresh air system, and the bathroom has exhaust system. So, how does the room deliver fresh air under normal pressure?

Generally, rooms in high-star hotels have two sets of independent pipes for air intake and exhaust. The air inlet is also a fresh air system, which sends in outdoor air through large fans (some with heat recovery), and then sends it to the fan coil units in each room for return air through fresh air pipes, and the mixed return air is sent out through the fan coil units. There is so little fresh air that most people can't feel it. In order to save electricity, some hotels don't even turn on new fans.