1.It takes certain amount of time for the alcohol in stomach to be absorbed into blood. To get a more accurate test result which can reflect the Blood Alcohol Content well, please abstain from smoking and drinking (for at least 20 minutes) before test.2.While doing breath sampling test, blowing cannot be interrupted (keep blowing about 5s). Blowing time is too short, the alcohol molecules in the blood cannot spread to the lungs completely, then test results will have a big difference from the blood alcohol content.