PROBLEM TO BE SOLVED: To provide an air-purifying apparatus in which a drainage tank is eliminated to simplify the configuration of the apparatus, thereby shortening the time period taken to clean a medial agent； and to provide an operating method.SOLUTION: A medial agent-feeding system 56 comprises two feeding parts: a feeding part 564 for preparation and a feeding part 566 for refilling, both of which feed a disinfectant solution to a circulation tank 54. A controlling device 700 performs a batch operation repeatedly with each cycle consisting of a normal operation mode and a preparation operation mode. In the normal operation mode, the disinfectant solution is fed from the feeding part 566 to the circulation tank 54 at a low refilling flow rate to maintain a set concentration of the disinfectant solution, while circulating the disinfectant solution stored in the circulation tank 54 among a circulation system 55, a spray device 54, a ventilation channel 52 for purification and the circulation tank 54. In the preparation operation mode, the old disinfectant solution in the circulation tank 54 is discharged from a discharge system 567 to the outside； and disinfectant solution having a new set concentration is prepared in batches in the circulation tank 54, while feeding the disinfectant solution at a high preparation flow rate from the feeding part 564 and while feeding dilution water from a dilution water-feeding system 563.SELECTED DRAWING: Figure 1【課題】排水槽をなくして装置構成の簡素化を図るとともに、薬剤洗浄を短時間で実施することができる空気清浄装置および運転方法を提供する。【解決手段】薬剤供給系５６は、殺菌剤溶液を循環槽５４へ供給する調製用供給部５６４と補給用供給部５６６の二つの供給部を有し、制御装置７００は、通常運転モードと調製運転モードとを１サイクルとするバッチ運転を繰り返し実施し、通常運転モードでは、循環槽５４に貯溜した殺菌剤溶液を循環系５５、噴霧装置５４、浄化用通気路５２、循環槽５４の間で循環させつつ、補給用供給部５６６から殺菌剤溶液を補給用小流量で循環槽５４に供給して殺菌剤溶液の設定濃度を維持し、調製運転モードでは、循環槽５４の古い殺菌剤溶液を排出系５６７から系外へ排出し、調製用供給部５６４から殺菌剤溶液を調製用大流量で供給するとともに、希釈用水供給系５６３から希釈用水を供給して循環槽５４に設定濃度の新しい殺菌剤溶液を回分調製する。【選択図】図１
