Apparatus for detecting a specific target odour comprises: a detector unit adapted to have removably associated therewith a holding unit for housing at least one insect in a predetermined position; means for exposing an insect in a holding unit associated with the detector unit to a sample of gas to be tested; and means for enabling monitoring of a response of the insect to the sample thereby to detect a response indicative of the target odour. In use of the apparatus, a holding unit housing at lest one insect that responds in a detectable manner to the target odour is associated with the detector unit. A sample of gas to be tested is supplied to the apparatus, for exposure to the insect or insects in the holding unit. The insect is monitored for a response indicative of the target odour, thus enabling determination as to whether or not the target odour is present in the sample. Because the holding unit is not part of the detector unit but is removably associated with therewith, the holding unit can be used to transport an insect or insects housed therein from a first, remote location, e.g. where insects are raised and conditioned, to a point of use at a second location where the detector unit is located. The detector unit may be a permanent or semi-permanent fixture at a point of use, or may be in the form of a portable unit. Also disclosed is a method of detecting a specific target odour.