In preferred aspect, the present invention features a membrane humidifier for a fuel cell which can control the amount of air flow and the amount of humidification based on the amount of water produced in a fuel cell stack according to a power level of the fuel cell stack while humidifying dry air and supplying humidified air to the fuel cell stack. The device may be used to condition a glazed portion of the pad, and then the conditioned pad portion may be used again for polishing. A client connects to the database server and issues requests on the connection, which initiates the execution of the data-tier application logic. The fluid ejection unit ejects a fluid onto an ejection target. When the controlling platform is abnormal or is abnormally connected to the controlling server, the controlling server continuously monitors the apparatuses in the building based on the stored real-time data of the controllers or the apparatuses.