Virtual breathalyser calculations BACscan® are based on a theoretical algorithm for determining blood alcohol concentration. The rate of absorption and excretion of alcohol from the body depends on many individual factors, so the results should be treated as indicative only. They cannot be interpreted as synonymous with the actual blood alcohol content. All responsibility and consequences of decisions made on the basis of calculations made with the virtual breathalyzer BACscan® are the responsibility of the person who uses it.