US Patent 8033532 Humidifier

A humidifier 10 has a water circuit 20 that switches the flow of water between a first flow state, in which hot water introduced from a first inlet 21 flows through a first heat exchanger 32 and flows to a first outlet 22 and in which cold water introduced from a second inlet 23 flows through a second heat exchanger 42 and flows to a second outlet 24, and a second flow state, in which the hot water introduced from the first inlet 21 flows through the second heat exchanger 42 and flows to the first outlet 22 and in which the cold water introduced from the second inlet 23 flows through the first heat exchanger 32 and flows to the second outlet 24. The water circuit 20 has a bypass passage 36 for connecting the inlets 21, 23 to the outlets 22, 24 respectively at the time of switching the flow of water. With this, even if the respective three-way valves 31, 33, . . . cause a faulty operation, the cold water and the hot water surely flow through the bypass passage 36 and flow to the respective outlets 22, 24.