To appropriately respond to state changes by monitoring, on a center side, the states of multiple hydrant apparatuses installed in a tunnel.

The multiple hydrant apparatuses 10 installed in the tunnel are monitored by a center device 14. A terminal unit 12 provided in each of the hydrant apparatuses 10 transmits state detection information created by detecting the state of the hydrant apparatus, to the center device 14. The center device 14 receives the state detection information transmitted from the hydrant apparatus 10 and notifies the content of the state detection information. The terminal unit 12 of the hydrant apparatus 10 detects, as the states of the hydrant apparatus 10, the states such as the presence/absence of a fire extinguisher, opening/closing of the door, a water feed pressure, a discharge pressure and a nozzle removing operation and transmits them to the center device 14.