Abstract: A detection system is disclosed for a mobile storage system which causes the storage system to prevent movement of a storage element whenever a person is detected in an aisle between storage elements. The detection system uses a presence or motion detector for detecting the presence of a person in an open aisle without direct contact between the person and the detection system. Preferably, a radar transceiver operating in X-band is positioned to overlie each open aisle to detect presence of movement of a person in an open aisle, even slight movement such as breathing. The storage system in which the detection system is connected prevents any closing movement of a storage element adjacent an aisle in which a person is detected so as to avoid frightening the person in the aisle.