Evaluation of tube position is important after in-hospital and prehospital emergency intubation. Colorimetric breath indicators are devices for immediate control of tube positioning by showing a color change according to end-tidal CO₂ (ETCO₂) concentrations. We hypothesized that colorimetric breath indicators can yield reliable results for confirmation of tube position. The aim of this study was to evaluate the effectivity and safety of a new colorimetric breath indicator (Colibri, ICOR AB, Bromma, Sweden) in 147 patients during general anesthesia, in critically ill patients, during transport to in-hospital interventions, and in a study design after insertion of a second tube into the esophagus in long-term ventilated patients. The Colibri was attached between the respective airway and ventilatory tubing. Seventy-three patients were investigated during general anesthesia, 39 patients were observed during long-term ventilation with an average duration of 33 hours, in 15 patients during transport to an intervention for up to 4 hours, and in 20 long-term ventilated patients at the medical intensive-care unit after insertion of a second tube intentionally into the esophagus with the help of a laryngoscope. The Colibri worked well in all groups investigated and showed no false results in the group with tubes inserted into the trachea and esophagus. Data suggest that the Colibri might serve as a valuable tool for evaluating and controlling tube position. This device is independent of power supply or electronic equipment, portable, small, and immediately ready for use.