Monitoring device for the room air pollution

The device has at least one fan that transports air into the room via a filter element(s) and an air impurity level sensor(s) connected to a controller. A characteristic field(s) for a defined time-related decrease in the impurity level is stored in a controller memory. The controller contains an arrangement that detects the impurity level, compares it with the characteristic field values and outputs a warning signal if there is a deviation. The device has at least one fan (14) that transports air into the closed room (10) via at least one filter element (18,24) and at least one interior space sensor (46) that detects the degree of impurity in the air and that is connected to a controller (34). At least one characteristic field is stored in a memory of the controller for a defined time-related decrease in the impurity level and the controller contains an arrangement that detects the impurity level, compares it with the characteristic field values and outputs a warning signal if there is a deviation.