A system for evaluating agricultural material in a passage, the system comprising: an imaging device for capturing a sequence of images that relate to agricultural material in a passage, wherein a lens or window of the imaging device faces an opening in the passage; a controller coupled to the imaging device, the controller comprising: a data port for receiving the sequence of images from the imaging device; and a processor, wherein the controller is configured to perform the steps of: determine an average image of the sequence of images; obtain a last image of the sequence of images; determine a difference between the average image and the last image to create a differenced image; using the differenced image, identifying candidate pixels in the last image that are stationary pixels or unchanged pixels; eliminate background pixels from the candidate pixels by thresholding pixels that fall within a colour range associated with an interior surface of the passage to produce an initial image mask of unchanged content identified in the last image; determine a mask area of the initial image mask; and generate an alert data message to inspect the imaging system if the mask area exceeds a threshold area. an imaging device for capturing a sequence of images that relate to agricultural material in a passage, wherein a lens or window of the imaging device faces an opening in the passage; a controller coupled to the imaging device, the controller comprising: a data port for receiving the sequence of images from the imaging device; and a processor, wherein the controller is configured to perform the steps of: determine an average image of the sequence of images; obtain a last image of the sequence of images; determine a difference between the average image and the last image to create a differenced image; using the differenced image, identifying candidate pixels in the last image that are stationary pixels or unchanged pixels; eliminate background pixels from the candidate pixels by thresholding pixels that fall within a colour range associated with an interior surface of the passage to produce an initial image mask of unchanged content identified in the last image; determine a mask area of the initial image mask; and generate an alert data message to inspect the imaging system if the mask area exceeds a threshold area. a data port for receiving the sequence of images from the imaging device; and a processor, wherein the controller is configured to perform the steps of: determine an average image of the sequence of images; obtain a last image of the sequence of images; determine a difference between the average image and the last image to create a differenced image; using the differenced image, identifying candidate pixels in the last image that are stationary pixels or unchanged pixels; eliminate background pixels from the candidate pixels by thresholding pixels that fall within a colour range associated with an interior surface of the passage to produce an initial image mask of unchanged content identified in the last image; determine a mask area of the initial image mask; and generate an alert data message to inspect the imaging system if the mask area exceeds a threshold area. determine an average image of the sequence of images; obtain a last image of the sequence of images; determine a difference between the average image and the last image to create a differenced image; using the differenced image, identifying candidate pixels in the last image that are stationary pixels or unchanged pixels; eliminate background pixels from the candidate pixels by thresholding pixels that fall within a colour range associated with an interior surface of the passage to produce an initial image mask of unchanged content identified in the last image; determine a mask area of the initial image mask; and generate an alert data message to inspect the imaging system if the mask area exceeds a threshold area.