A method of monitoring a hazardous zone (2) and a safe optoelectronic distance sensor (1) for monitoring a hazardous zone (2) at a movable machine part (3) having a protected zone (4), wherein the safe distance sensor (1) is arranged at the movable machine part (3), wherein a tool (5) is arranged at the movable machine part (3), wherein a plurality of distance sensors (1) are arranged in a modular manner and wherein the protected zone (4) is adapted to the tool (5).