Environmental applications of odour sensing technology have been limited by problems of achieving stable measurements when confronted with highly variable environmental factors. We present three case studies for odour sensor technology applied to (a) detection of dry rot in buildings using a sampler and preconcentrator based on solid phase microextraction coupled to a metal oxide sensor array; (b) continuous monitoring of the odour of waste water; (c) discrimination of volatiles emitted by fires in the development of a smart fire alarm system. Each of these applications has required understanding of the nature of the volatiles to be detected and discriminated, specific sampling methods and dedicated sensors, electronics and software.