NOVELTY - A purifier has supplier for supplying gas containing nitrogen group offensive odor component (2), into a gas absorption tank (1) filled with filler, into which nitrification microbe and microorganism are adhered. Microorganisms decompose amines contained in waste gas into ammonia, and nitrification microbe converts ammonia into nitrous acid (NA) or nitrate nitrogen (NN).    USE - For purifying nitrogen group offensive odor component containing gas such as monomethyl amine, dimethyl amine, trimethyl amine and ammonia generated from sewage sludge compost.    ADVANTAGE - The purifier converts nitrous acid or nitrate nitrogen into nitrogen gas without neutralization method. The apparatus structure is simple and the apparatus is used as deodorizing apparatus, thereby reducing expense. The gas containing nitrogen group offensive odor component is purified efficiently and hence further treatment is avoided.    DETAILED DESCRIPTION - A purifier has supplier for supplying gas containing nitrogen group offensive odor component into the tank (1). The absorption tank is filled with filler, into which nitrification microbe and microorganism are adhered. The microorganism decomposes amine contained in waste gas into ammonia, and the microbe nitrifies the ammonia into nitrous acid (NA) or nitrate nitrogen (NN). A water sprinkler is provided to elute NA or NN by sprinkling water to the tank. An ejector for ejecting water (which dissolves NA or NN) from the tank (1) and another ejector which ejects gas so that deodorizing is performed to form NA or NN water, are provided in the tank. A water supplier for supplying water into a denitrification tank (6) arranged with filler, is provided. Biodegradable plastics and denitrifying bacteria adhered to the filler reduces NA or NN to nitrogen. An elimination unit which ejects nitrogen and water from the tank (6) after denitrification, is also provided.    An INDEPENDENT CLAIM is also included for purification of gas containing nitrogen group offensive odor component. A waste gas is supplied into the tank (1). The microorganism decomposes amine contained in waste gas into ammonia, and the microbe nitrifies the ammonia into NA or NN. NA or NN is dissolved in water and introduced into tank (6) arranged with filler. The biodegradable plastic and denitrifying bacteria adhered to the filler reduces NA or NN to nitrogen which is ejected from the tank.    DESCRIPTION OF DRAWING(S) - The figure shows the explanatory drawing of water gas purifier.    Gas absorption tank (1)    Nitrogen group offensive odor component containing gas (2)    Denitrification tank (6)    Circulating pumps (8,12)