Modern work environment is changing from classic physiological to more psychological workloads. The capability to monitor biochemical processes within the human body positions breath analysis as a promising method to non-invasively and quickly detect mental stress. The present work aims to identify psychological stress biomarkers and breath profile changes after psychological interventions (PASAT or relaxing videos). In an exploratory study, 14 male participants followed a double cross-over randomized study which included two experimental sessions (stress and neutral/relax). GSR and HR were continuously measured to indicate physiological stress levels. NASA-TLX questionnaires were fulfilled to quantify individual stress. Breath samples were selectively collected by a recently developed advanced breath sampling prototype device and afterwards analyzed with a GC-IMS apparatus. Some promising results on mental stress detection were found and are presented and discussed in this paper.