A method for monitoring the interior of a vehicle including emitting electromagnetic waves of at least one frequency or at least one frequency band towards at least one seat arranged in the interior of the vehicle by means of an electromagnetic radiator, receiving reflected electromagnetic waves by means of a sensor, detecting a living object on the seat from the received reflected electromagnetic waves by means of a detection device, determining a volume of the detected object from the received reflected electromagnetic waves by means of the detection device, determining a weight characteristic of the detected object on the basis of the determined volume of the object by means of the detection device, outputting a detection signal representing the weight characteristic by way of the detection device, and actuating a safety system to make the interior safe in accordance with the detection signal.