Underground stations and their connected underground sections, entrances and exits with a length of more than 20 meters, and independent underground sections with a length of more than 500 meters should be equipped with indoor fire hydrant water supply systems. Mechanical smoke exhaust facilities should be set up for underground station equipment and management rooms with a total area of more than 202 square meters or more than 50 square meters, single rooms where people often stay, inner walkways with a linear distance of more than 20 meters from the farthest point to the public area of the station, underground passages with a continuous length of more than 60 meters, entrances and exits, etc.
Subway is a kind of fast, large-capacity and electric traction rail transit built in cities. Trains run on fully enclosed lines, the lines located in the central city are basically located in underground tunnels, and the lines outside the central city are generally located on viaducts or on the ground. The English name is metro (Underground Railway). Subway is a high-density and large-capacity urban rail transit system, covering all kinds of underground and above-ground road rights in urban areas. The subway in Taiwan Province, China Province is called "MRT". In addition to the subway, it also includes elevated railways or railways laid on roads. Therefore, the subway is the exclusive right of way, and there is no grade crossing, which is also the fundamental sign that the subway is different from the light rail transit system. The earliest (and first) subway in the world is the Metropolitan Subway in London, England, which was built at 1863.