A supply cabinet is fitted with an outer sensor and an inner sensor. The outer and inner sensor wirelessly sense inventory items tagged with radio frequency tags and in proximity of the sensors. A method of tracking inventory items stored in a supply cabinet includes determining, based on time sequencing of sensing by the outer and the inner sensor, if an inventory item was removed from the cabinet or stored into the cabinet, and updating an inventory database accordingly. An alarm is optionally triggered if an inventory item is removed by an unauthorized user.