The area of operation of UAS (Unmanned Aircraft Systems) has increased substantially due to falling prizes and increased on-board computational power. Many of these applications are intended to increase the safety of the civil population or to support disaster operations. One of these applications is the measurement of the concentation of toxic gases after an incident in a chemical plant to estimate the release rate. The optimal distribution of the agents of the swarm equipped with pollution sensors in the area to be scanned is an important challenge. The communication between the individual agents as well as with the ground station is limited. Furthermore, a simple function allows a weighting of a distinguished part of the area to be scanned. This paper presents technical basics and a simple, decentralized but yet effective on-board implementation as well as results in simulation. © 2012 Springer-Verlag.