DAPCI (Direct Ambient Pressure Chemical Ionisation) is a novel, handheld ambient ionisation source that can be used stand alone or coupled to a mass spectrometer for analysis a broad range of compounds. An important application is the detection of drugs and explosives at important border security checkpoints. However the ionisation mechanism and ease of use leads means it has the ability to perform ambient analysis in a variety of fields in user selectable both positive and negative ionisation modes.