The present invention relates to an air purifier capable of automatically removing noxious gases generated in a closed space of various industrial sites including a semiconductor production site, and more particularly, to an air purifier for filtering various fine dusts and dusts, It removes harmful elements in the air through thermal catalytic reaction. Secondly and tertiaryly removes harmful viruses and germs from the air through sterilized water supply and ultraviolet light irradiation to maintain pleasant indoor air and prevent air pollution. And to provide an industrial air purification device that can be used. The present invention relates to an exhaust pipe (110) extending from an indoor to an outdoor space； An exhaust fan 120 installed at a part of a discharge end of the exhaust pipe 110； A main damper (130) installed in one part of the exhaust pipe (110) and opened and closed to control an air flow direction； And a gas detection sensor (140) installed on a part of the exhaust pipe (110) to detect whether or not a noxious gas is generated. A suction unit 211 for receiving air containing harmful substances and a discharge unit 212 for discharging air from which harmful substances have been removed are formed integrally with each other so as to be able to circulate air from the exhaust pipe 110. [ Shaped manifold 210； An intake damper 220 installed in the intake unit 211 to open and close the intake damper 220； An exhaust damper (230) installed in the exhaust part (212) and operated to open and close； A fine metal filter (240) installed at both ends of the catalytic filter part (250) inside the branch conduit (210)； A catalytic filter part 250 disposed between the pair of fine metal filters 240 and filled with an adsorbent and a catalyst to remove harmful components captured by the adsorbent through a thermal catalytic reaction； A heating unit 260 for transmitting heat to the catalytic filter unit 250； A heat insulating means 270 formed to surround the catalyt
