A portable sensor system for the detection of human volatile compounds against transnational crime

•Humans emits characteristic sign-of-life volatile organic compounds.•Types and concentration ranges of specific volatiles have been characterized using different gas sensors.•A portable sensor system was developed to determine human presence within a few minutes of direct measurements in the field.•Gas emission measurements complement current detection methods used by search and rescue teams.•Recognition of trapped and / or hidden humans with a higher level of confidence. Human smuggling accounts for a significant part of transnational organized crime, creating a growing threat to national and international security and putting at risk the health and lives of the people being smuggled. Early detection and interception of human beings hidden in containers or trucks are therefore of considerable importance, especially at key transportation hubs, such as at international borders and harbors. The major challenge is to provide fast inspection procedures without needing to open sealed trucks and containers. The detection of trace key volatile organic compounds, which includes aldehydes and ketones, emitted by humans can be used to rapidly determine human presence, requiring only several ml of air to be taken from inside a container. In this paper, we describe a prototype portable device for the rapid detection of hidden or entrapped people, employing a combined ion mobility spectrometer and sensor array system for obtaining a volatile signature of human presence. The detection limits of this combined analytical device are sufficiently low for use in sensing ketones and aldehydes being emitted by humans in closed containers. For easy handling by security personnel, a classification algorithm is applied that provides a simple YES or NO decision. With a training dataset of more than 1000 measurements, the algorithm achieved an area under curve of 0.9 for untrained scenarios. The field measurements show that two people need to stay in a car for between 20 and 30 minutes in order for the emitted trace volatile organic compounds to reach concentrations high enough for reliable detection with our analytical device.