The present invention relates to a decentralized hybrid ventilation system configured for inletting air into a room and for outletting air from a room. The ventilation system comprises a housing having an inlet channel and an outlet channel. A first fan is arranged in the inlet channel for providing an airflow into the room and a second fan is arranged in the outlet channel for providing an airflow out of the room. A heat exchanger is arranged in said channels for exchanging heat between air flowing into the room and air flowing out of the room and an air filter is arranged in each channel configured to filter air flowing into the heat exchanger. Furthermore, the ventilation system comprises a first service door and a second service door each providing, when open, an opening between the room and one of said channels to diverge the airflow from primarily flowing through the air filters and/or heat exchanger. The ventilation system also comprises a control system configured for switching between different modes of operations, wherein during a first mode of operation, the first and second service doors are both closed; during a second mode of operation the first and the second service doors are both open; and during a third mode of operation, one service door is open and the other service door is closed.