A new finger-touch testing device is now ready for launch, which can give a red or green light for alcohol in the blood stream in just 10 seconds, allowing for the “processing” of up to 300 employees per hour. According to the manufacturers, users can set their own threshold levels and the device can be used for industries from transport and leisure to the National Health Service and banking. This device begs the question of what to do with an employee who got a red light. The problem lies in identifying what a red light actually means, and then establishing some connection between the alcohol level and the job. What dictates fitness to perform a role is not the precise level of alcohol in the system, but each individual’s physiological response to it. Therefore, the employer may find that it is taking action against red-lighters who are far more physically capable than some greens who have only a few milligrams of alcohol less coursing round the system. Blood-alcohol readings may be affected by weight, body mass index, gender and parallel medications or oral contraceptives. Employers considering using the system as a deterrent will have to bear in mind that their own credibility and their ability to rely on the results will depend upon their setting a suitable threshold level. If set unrealistically low, you might as well not bother.