Abstract: A procedure and a filter device (1) serving the purpose of removing and/or destruction organic substances in contaminated air. The filter device comprises at least one ventilator (12) for sending an air stream through a first chamber (14) with an opening, which is connected with a source for contaminated air; a second chamber (15) with a number of sheets (20) placed abeam the main direction of the air stream in order to make the air stream change direction at least one time; a third chamber (16) with a number of perforated tubes (22) which at least at one end are in open connection to a secondary air source; a fourth chamber with a number of lamps for radiating the air stream with a short-waved ultra-violet light and; a fifth chamber (17) with a volume, which gives the air stream a predetermined duration time in the chamber, and which has an opening, through which the purified air passes in order to be released to the surroundings.