The blood alcohol level represents the volume of alcohol in the blood and is measured in grams of alcohol per litre of blood (g/l) or its equivalent in exhaled air.
According to current legislation, the blood alcohol levels allowed for drivers in Spain are the following: 0,5 g/l for general drivers, 0,3 g/l for professional drivers.
Even below the legal limit, the risk of incident may already be increased. Therefore, it is best to avoid driving after consuming any amount of alcohol. The only truly safe rate is 0.0 g/l.
The blood alcohol level you reach after consuming alcohol can vary greatly. Therefore, even if you think you know your limits, it is really easy for alcohol to surprise you. It is always best not to drink alcohol at all if you are going to drive.
After ingestion, alcohol is absorbed in the digestive system, approximately 20-25% in the stomach and most in the small intestine, from where it passes into the blood, reaching the highest concentration after 30 – 90 minutes. The absorption rate can be modified by:
- Food: the presence of elements in the stomach delays absorption.
- The type of drink: both distilled drinks and mixtures with carbonated drinks are absorbed faster.
- The elapsed time: at the beginning of the intake, it is absorbed faster.
- The degree of habituation or tolerance. Chronic heavy drinkers absorb alcohol more quickly than abstainers.
After absorption, the blood distributes the alcohol throughout the body. We call the amount of alcohol present in the blood the blood alcohol level, the higher the level of alcohol in the blood, the greater the effects on driving.
After absorption, most of the alcohol (90-98%) is metabolized in the liver at a constant rate and another part is eliminated unmetabolized through urine, sweat and exhaled air.
It is the determination of alcohol in exhaled air that is used in breathalyser controls, taking advantage of the fact that there is a constant 2001/1 relationship between the level of alcohol in the blood and the level in exhaled air. The measurement is carried out using a device called an alcohol meter, making the method bloodless, comfortably, and reliably.
In expelled air, the limits are 0,25 mg/l for general drivers, 0,15 mg/l for professionals. Again, the only safe limit is zero.
Another way to know the blood alcohol level is by determining the level of alcohol in the blood, a test that is used in those cases in which the interested party says they cannot perform the test in air due to suffering from an illness that prevents them from blowing, or in injured persons, or in those cases in which the interested party requests a contrast test, the extraction will be carried out in a health centre.
