The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is an international treaty, still being ratified, that bans all nuclear tests. An important ingredient to the test is monitoring, whether nuclear tests will be performed nonetheless. To this end, the CTBT Preparatory Commission has established a world-spanning monitoring system that relies on seismic, hydroacoustic, infrasound and radionuclide monitoring. In this episode, our guest is Randy Bell who runs the international data center and is thus responsible for running the monitoring network and evaluating the collected data.