Abstract: In a method for detecting smoke or fire in rooms, at least one image of the room is recorded and digitalized to a digitalized image. The digitalized image is compared to a reference image in digitalized form, wherein the reference image is generated based on an image of the room previously recorded and digitalized. The sum of image elements of the digitalized image deviating by at least one first threshold value from the reference image is determined. An alarm signal is generated when the sum reaches or surpasses a second threshold value. The device for performing the method has a video camera and a matching light source arranged in a dark field arrangement.