Accuracy Safe_Drive has been tested in many countries for accuracy in'cludilng German standard 'TUV' , and has been awarded the European CE mark of quality. Safe-Drive retains accurate calibration for a minimum of 6 months when used every day and is maintained for much longer periods when used infrequently. Accuracy is 90% or better in most of situations. SaSafe-Drive will notify you if the battery is low, the operation light will become red (instead of green) and will soon cease to function until a new battery is installed. Limitations Any device measuring a tolerance of 0.01 of blood alcohol concentration from a breath is not 100% accurate, and is subject to variation. Even the police units are not sufficient for a conviction, only an actual blood test is 100% accurate. The unit may not clear (all indicators extinguish) if the ambient air is contaminated, such as a smoky bar. Results will not be accurate when all indictor lights are not extinguished. If the sensor loses its accurate calibration (if dropped hard, damaged or exposed to excess heat or moisture) it will register a very high reading and will no longer be a reliable guide.   Allow at least 20 minutes after consuming alcohol before using the blood alcohol detector.  This ensures the breath sample is taken from your lungs, not from the alcohol in your mouth, which may result in a higher reading.