The detection of respirable asbestos fibres in the ambient environment has grown in importance as the health risks associated with this material have become more fully understood. However, there is no real-time method of identifying airborne asbestos in situ. A light scattering instrument allowing the detection of respirable asbestos has been constructed. It captures data relating to the spatial distribution of light scattered by single particles in flow using a photodiode array containing two concentric, segmented detector rings. The data allows real-time categorization of airborne particles accordingly to their shape (Kaye et al. 1997). However, discrimination on the basis of morphology alone can lead to misclassification - most notably to false positive identification of asbestos. To overcome this problem, the system has been enhanced to take advantage of magnetic properties of asbestos, which are virtually unique among respirable fibres.