Abstract: A detector access chamber (10) for a wireless directional detector (40), comprises a hollow body (12) having an open a upper end (20) and a lower end (24) at an opposing end, a lid (16) engageable with the open upper end (20) of the body (12) and preferably adapted to accommodate at least a 40 tonne vehicular load, and a detector holder (38) within the body (12) to hold a wireless directional detector (40). In use, the lid (16) and the detector holder (38) together define a volume adapted to constrain internal reorientation of the wireless directional detector (40) caused by vibrations. A submergible detector system (42) is also provided.