Certain work areas include mobile machines and pedestrians working closely together. Both must be present at almost the same time. Facilities are sometimes configured so that safe spots or safe areas are within the work area where a pedestrian can retreat to be safe. However, this provision is only useful if the pedestrian recognizes the need to retreat to the safe area and moves into the appropriate safe area, which, unfortunately, does not always happen. With a proximity detection system installed on the machines and with pedestrians equipped with Personal Alarm Devices, the pedestrians will be warned when a machine is dangerously close and the operator will also be warned—even if the pedestrian is in the designated safe area. Nuisance alarms will frequently be given even when there is no danger because the pedestrian is positioned behind a barrier. The solution is to equip the safe areas with a Silent Zone Field so that when the pedestrian is in a safe position within the silent zone fields, the proximity detection system will not give a warning to the pedestrian or the operator. Silent Zones can be produced with magnetic fields in multiple ways as is disclosed in the Patents # 8,446,277 and 8,810,390. While it is recognized that it is critical to use stable, precise magnetic fields for defining hazardous zones, it is also critical to produce Silent Zones that are stable and precise. Otherwise, nuisance alarms will result. Thus magnetic fields are the best solution.