For reducing energy consumption of sensor nodes in wireless sensor networks (WSNs), previous studies have proposed an approach in which some of the nodes are active, while the others are inoperative and the nodes switch between these two states as and when required to ensure full coverage of the area of interest. However, previous schemes for active node selection required the location of each sensor node to be known. This study presents a density control algorithm which can ensure full coverage without the need for this information. Additionally, when applied to a system with coverage holes, the scheme is capable of detecting and wadding these holes. The simulation results show that the scheme guaranteed 100% coverage of the target area using a comparable number of active nodes as that specified by algorithms which require location data.