Luminescence-based detection of organic vapours with an organic semiconductor has attracted much interest because of its potential for detectors that have high sensitivity, compact form factor, simple operation and low-cost. At COPE we have developed sensing materials that can detect a range of explosive organic vapours and demonstrated sensing with a handheld detector called Arbsense. Arbsense is about the size of an apple, weighs around 200 g, and is controlled with an Android-based App. While developing sensing materials for different organic vapours is critical at COPE we also have developed bespoke methods of understanding the interactions of the vapours with the sensing films, which has been critical for the demonstration of their efficacy.