We present work on the development and testing of a low-cost wireless chemical sensor network (WCSN) for monitoring irritant/toxic gases in the environment. The WCSN used in this work takes advantage of recent advances in low power wireless communication platforms and uses colorimetric sensors to detect the presence of certain target gases. This sensor network adopts a star configuration and performs one way RF communications from individual sensor nodes to the base-station. Each node in the network is composed of a multiple sensor platform that measures light intensity, temperature and motion. The light sensor was used as the chemical sensing platform in such a way that the node is housed in a specially constructed sealed container that has a colorimetric chemical sensing film coated PMMA window aperture directly above the light sensor. The light intensity reaching the light sensor is modulated by changes in the colour of the sensing film and such changes indicate the presence of chemical plumes. © 2008 IEEE.