The outdoor fire hydrant is a water supply facility set on the fire water supply pipe network outside the building. It is mainly used for the fire truck to take water from the municipal water supply network or the outdoor fire water supply network to put out the fire. It can also be directly connected to the water hose and water gun to put out the fire. Therefore, the outdoor fire hydrant system is also one of the important fire-fighting facilities for fire fighting.

Fire hydrants should be placed in public shared spaces such as corridors or halls. Generally, they will be placed in the walls of the above spaces. They cannot be decorated. They should be clearly marked ("fire hydrants"), and obstacles should not be set in front of them to avoid affecting the opening of fire hydrant doors. The fire hydrants are generally not set in the room (such as the box), which does not comply with the fire protection regulations and is not conducive to the timely rescue of the firefighters.