An exemplary method for monitoring a package on a conveyor may include emitting a plurality of infrared beams, detecting one or more of the emitted infrared beams, calculating a package height using the detected infrared beams, determining whether the package height exceeds a predetermined threshold, and when the package height meets or exceeds the predetermined threshold, sending a signal indicating a height of the package exceeds the predetermined threshold. A package size detector may include a transmitter including a plurality of light sources and positioned on a first side of a conveyor, and a receiver positioned on a second, opposite side of the conveyor, including a plurality of light sensors, each of the plurality of light sensors being configured to detect light emitted from the plurality of light sources. A controller may be configured to determine whether a package height exceeds a predetermined threshold.