Regulatory bodies are increasingly expressing an interest in the monitoring of the work-place air for hazardous biochemicals but examples in the literature of this form of monitoring are not common. In contrast, there are many examples of sensitive assays being developed for the quantitation of very small quantities of biochemicals in fluids which use a multi-step process. An aerosol sensing system has two components : an aerosol collection device and the biochemical detector. The coupling of the two has rarely been investigated. The requirements for such a sensing system are reviewed, together with an appraisal of the types of detector devices that might be suitable. It is suggested that there is a need to develop onestep sensitive sensors for real-time aerosol monitoring.