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Frequently asked questions about testing for alcohol

ALCO-Safe's experts answer many of the questions that we regularly get asked about alcohol in the body, testing for alcohol in the breath, and breath analysis equipment.

The alcohol we drink is called ethanol. It has the chemical formula C2H5OH, and is made by the action of yeast on sugars in a process known as fermentation. It is a small, simple molecule, and is highly soluble in water: this means it requires no digestion, so absorption into the blood goes by the process of simple diffusion.

NO: this is a common myth. In fact it is a depressant, which exerts its characteristic effects on the body by slowing down the electrical processes in the central nervous system. Some of the effects noticed during intoxication, and which might appear to be a result of stimulation, are, however, generally a result of the depression of shyness and those social inhibitions that normally control our behaviour.

Apart from perhaps making the taste of the drink more pleasant, it is also a matter of absorption.

Alcohol is absorbed from the stomach and small intestine in response to a concentration difference between the fluid in those organs and the blood. The larger the concentration difference the greater the rate of absorption – but only up to a point. A neat spirit will contain between 37 and 40% alcohol by volume, and when taken undiluted it can actually slow down the rate of absorption, principally by slowing down the rate of gastric emptying. This is because alcohol is most easily absorbed through the upper section of the duodenum than it is through the stomach. So if the spirit drink is diluted to about 50:50 with water, gastric emptying is more frequent and the alcohol is absorbed into the body more quickly. Also, gas in a mixer [such as soda, tonic water or coke] will speed up alcohol absorption. The mechanism by which it does this is not fully understood, although it is probably because the gas also speeds up gastric emptying – which is why we often use such mixers to dilute spirits drinks.

The alcohol in a drink such as champagne, gin and tonic or whisky and soda or even a glass of sherry, is absorbed into the blood quite rapidly; especially when the drink is taken on an ‘empty stomach’. This decreases the blood sugar level and so triggers the sensation in the brain that we identify as hunger. This is known as the aperitif effect.Such a drink, especially when then followed by a glass or two of wine with the meal itself, also has the effect of increasing the secretion of saliva and gastric juices: this aids the process of digestion.

YES and NO: fatty foods will slow down alcohol absorption quite significantly, as they effectively form a lining that it cannot easily pass through [alcohol is not soluble in fat].

However, food in the stomach will also considerably speed up the rate of gastric emptying. This means the alcohol comes more quickly into contact with the walls of the upper section of the small intestine [the duodenum], through which it is absorbed far more efficiently into the blood than it would be though the walls of the stomach.

NO: most [about 90%] of the alcohol we drink is broken down in the liver. This organ works at its own pace, and there is simply nothing you can do to speed it up. Once you have had a drink and the alcohol has been absorbed into your body, the only thing that will get rid of it is …. TIME!

NO: alcohol is only soluble in body water, it does not mix with fat. But because a woman’s body has about 15% more fat than a male’s, they have proportionately less water to dilute the alcohol. This means they will reach a higher level of breath/blood alcohol than a man would, of the same body weight, if they were both to consume the same amount of alcohol under identical conditions.

So far as alcohol elimination is concerned, because a woman’s liver is slightly larger per body weight than a man’s, females generally metabolise alcohol slightly faster than males.

NO: it is not generally possible to eat sufficient such foodstuffs to generate a breath or blood alcohol level of any forensic significance.

NO: it is not possible to achieve a measurable level of alcohol in the body by even the prolonged inhalation of very strong vapours of alcohol.

NO: it is not possible for alcohol to be accumulated in the body as a result solely of its passage through the skin.

NO, it is NOT true! Alcohol always impairs driving performance, even in small amounts. There is never an improvement in the required skills, except perhaps [and often] in the mind of the driver him or herself!

Except in several, very extreme cases, NO. The conditions inside the body are not at all right for fermentation, and even the very small amounts that are produced in this way are rapidly broken down by the enzymes in the liver, so that the concentration of alcohol does not increase. In fact, the highest level of breath alcohol that can be reached without drinking the substance is generally regarded as about 3µg/100ml [0.03mg/L].

Further, a simple consideration of the chemistry and resulting physiology involved will show that, even if the fermentation process was able to proceed inside the body in the first place, the amount of sugar that would have to be converted in order to reach and then stay at an alcohol level of any clinical or forensic significance is so large as to be inconceivable. There would also be a huge amount of carbon dioxide gas generated as a by-product of the fermentation reaction process!

ALCO-Safe Highlights

  • 42 years of experience in manufacturing, distribution and support
  • Supplier of equipment and development of substance abuse programmes
  • Sole distributor for LION breathalysers
  • Representatives of Abbott Toxicology for drug detection equipment.
  • Abbott Toxiciology in brief:
    • 2 world-class laboratories
    • Over 10 million tests per year
    • Over 5,000 customers in 75 countries



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