An alcohol interlock is a system comprising a breath alcohol measuring instrument and an immobiliser which may be easily installed in motor vehicles as passenger cars, coaches, taxis, hazardous goods transporters, lorries, trams, trains, motorcycles, boats, or snow mobiles. Before the vehicle motor can be started or the vehicle can be moved, a breath sample has to be provided to the alcohol interlock, normally through a mouthpiece. Once the breath alcohol measurement has been performed, the alcohol interlock will prevent drivers from starting the motor if they have an alcohol concentration above a predetermined limit value. This limit may be set at the legal limit of a respective country or lower. Alcohol interlocks that meet the relevant European Standards detect, for example, if the sample is delivered by a human being. They are also capable of preventing and detecting tampering with the instrument. Additional parts of the system may include identity checking or recording mechanisms. The purpose of this European Standard is to give practical guidance for selection, installation, use and maintenance of alcohol interlocks. It is directed to all those who have an interest in alcohol interlocks as well as companies selling and installing alcohol interlocks, purchasers and users for commercial, professional or private use. The European Standard gives information about the alcohol interlock and how it is to be used. This European Standard describes alcohol interlocks for use in vehicles as a general preventive measure in traffic safety as well as for use in drink driving offender programmes. However, information provided may also be useful for alcohol interlocks in other applications.