With the ACE alcohol test tube you can quickly and easily determine your breath alcohol content. These test tubes are approved for self-testing according to French legislation, they are for single use only. The test tubes work like a chemical breathalyzer and provide results on the estimated breath alcohol content, which can be used as a guide. The tester consists of a glass tube in which a crystallized reagent is enclosed. The function of the reagent is to indicate the alcohol content in the exhaled air by changing color from the original yellow to green, with the length of the change in color proportional to the alcohol content.