System for detecting and reducing ethylene (1) in a storage room (2) or a reefer container (2), comprising a sensing reaction chamber (10) and a ethylene/ozone reaction chamber (19) in fluid communication with the storage room (2), in which ozone and air from the storage room (2) is brought into reaction with each other, an ozone generator (6) and light detecting means (8) for detecting light emitted via reaction between the ozone and ethylene, said light detection means producing detection signals (12), processing means (9) and airstream means (4) for forcing an airstream through the system (1). The system (1) is adapted such that ozone excessive from the reaction between the ozone and the ethylene in the sensing reaction chamber (10) with the light detection means (8) is lead into the airstream to the ethylene/ozone reaction chamber (19), and that the ozone generator (6) is controlled by the feedback signal (13).
