How Do Alcohol Breathalysers Work?

So just how can your breath show how much alcohol you have consumed? Alcohol you drink shows up in the breath because it gets absorbed from the mouth, throat, stomach and intestines into you bloodstream. Alcohol is not digested upon absorption or chemically changed in the bloodstream. As the blood goes through the lungs, a calculable amount of the alcohol will move across the lung membranes and into the lungs themselves. Once this alcohol is in contact with the air in the lungs, it evaporates and is exhaled. The concentration of the alcohol exhaled from your lungs is directly related to the concentration of the alcohol in your blood.

Alcohol Breath Tests

By breathing air exhaled from deep within you lungs onto an alcohol sensor then you can simply measure how drunk you are. A deep and continuous breath is required to make sure air is properly taken from your lungs. Some people may try and think they can cheat the system by giving a slow of shallow breath from the mouth but if you have recently consumed alcohol, and it's still present in your mouth, then this would actually give a higher reading!

Alcohol Permille Reading

Breathalysers will generally give a reading marked at BAC - this is your blood alcohol content which you may remember has a legal UK drink drive limit of 80mg per 100ml. This will give a reading of 0.08 %BAC or to save on decimal places 0.8‰ BAC (percentage per thousand) so this is the figure you are looking to stay under. Remember however that this is only a guide, and that the police have the final say with taking you down the station for a blood or urine test to confirm their own breathalyser readings.