Silicon micromachining technologies have been used to develop metal oxide gas sensor elements with very small heating power consumption. With the power consumption of a single micromachined sensor element being an order of magnitude less than that of commercial thick-film devices, novel kinds of gas sensing systems become feasible, which allow higher selectivity, lower drift and built-in self-test functionalities to be realised within the power budget of a single thick-film gas-sensing element. Such systems can be built up using components from an emerging MEMS toolkit for miniaturised gas sensing systems. The article presents components of this toolkit and points out system functionalities that can be achieved by combining elements from this kit. (C) 2003 Elsevier Science B.V. All rights reserved.