Provided is a method of recognizing information on a filter unit mounted on an air purifier of a respirator wherein the air purifier and the filter unit of the respirator which filters polluted external air and supplies purified air to a worker are wirelessly interconnected such that a control unit of the air purifier may provide the worker with information on the filter unit such as a type, a load rate depending on a blockage degree of the filter unit, a final operation time, a residual operation time, and a replacement time of the filter unit through information data transmitted from the filter unit. It is possible to precisely recognize the filter unit appropriate for a workplace and a work environment, thereby preventing an error, failure, and malfunction of the filter unit and simultaneously with continuously working. The air purifier and the filter unit are wirelessly interconnected through radio frequency identification (RFID), wireless fidelity (Wi-Fi), near field communication (NFC), Bluetooth, or Zigbee to detect a type of a filter, recognize information of the detected filter such as an operation time and life thereof by counting an operation time of the filter, and allow a wearer to recognize the information.