This easy-to-use breathalyzer uses background illumination for the mouthpiece slot as well as the display. You can thus also take a test in dark surroundings.The AF-33 includes a high-quality fuel cell sensor with an accuracy of 97.9% (according to a study conducted by the Technical University of Vienna).Examined by Technical University Vienna!!!Accuracy according to the alcohol tester accuracy study of the Vienna University of Technology dated October 2015. 5 measuring reference points (0.00,0.10,0.25,0.40 and 0.60 per mil) were tested in the laboratory with 5 identical measuring devices and 10 repetitions (excluding the manufacturer). In total, the device type was tested 250 times in the laboratory of the Institute for Analytical Chemistry at the Vienna University of Technology under the direction of Professor Dr. Erwin Rosenberg.The details of the study can be found at "Documents & Downloads" (in German).