Fire hydrant, a fixed fire fighting tool. The main function is to control combustible materials, isolate combustion-supporting materials and eliminate ignition sources. Fire fighting systems include outdoor fire hydrant system, indoor fire hydrant system and fire extinguisher system, and some will also have automatic sprinkler system, water cannon system, gas fire extinguishing system, fire detection system and water mist system. Fire hydrants are mainly used for fire engines to take water from municipal water supply network or outdoor fire water supply network to extinguish fire, and can also be directly connected with hoses and water guns to extinguish fire. Therefore, the outdoor fire hydrant system is also one of the important fire fighting facilities.