Simultaneous removal of acetaldehyde, ammonia, and hydrogen sulphide from air by the impregnated active carbon was studied at 25-degrees-C. p-Aminobenzoic acid (PABA), phosphoric acid (H3PO4), and metal compound such as copper (11) chloride dihydrate (CuCl2.2H2O), copper (II) nitrate trihydrate (Cu(NO3)2.3H2O), and potassium iodide (KI) were investigated as impregnation ingredients. Acetaldehyde and ammonia were simultaneously removed from air by the active carbon impregnated with PABA and H3PO4. The removal was found to be made mainly through chemical reaction. Acetaldehyde, ammonia, and hydrogen sulphide were simultaneously removed from air by the active carbon impregnated with PABA, H3PO4, and metal compound such as CuCl2 . 2H2O, Cu(NO3)2 . 3H2O, and KI.