How Do Breathalyzers Work?
Breathalyzers provide a useful, noninvasive technique by which you can identify whether or not you are over the drink drive limit and judge whether or not you are safe to drive. Breathalyzers determine drunkenness in objective terms, based on the blood alcohol concentration (BAC) in the driver's blood.
What is BAC (Blood Alcohol Concentration?
The UK legal limit for drivers is 80 mg of alcohol per 100 ml of blood, often referred to as a BAC or blood-alcohol concentration. In US terms this would be expressed as 0.08%. This is alternatively expressed in terms of breath alcohol - 35 µg (microgrammes) per 100 ml (which is now the usual official measure in the UK), or alcohol in the urine - 107 mg per 100 ml.
This is often reckoned to be equivalent to two pints of ordinary strength beer which, for a man of average weight, is broadly true, but should not be used as a general rule - see Drink-Driving Guidelines. It is impossible to draw an accurate correlation between the amount of alcohol consumed and the resulting peak BAC, and anyone trying to "drink up to the limit" runs a serious risk of exceeding it.
It is also possible to be charged with driving or attempting to drive under the influence of drink or drugs even with a BAC level is below 80 mg. Such cases are rare but not unknown. In addition, a BAC level not far below 80 mg is likely to be regarded by the courts as an aggravating factor if charges are brought for causing an accident.
Determining BAC using a Breathalyzer
How is it possible to determine the level of alcohol concentration in the blood by using a person's breath? Unlike other liquids such as fruit juice or milk, the body does not digest alcohol. Instead, it is absorbed through the lining of a a person's mouth, throat, and internal organs
Once the body has absorbed the alcohol, it then passes into the blood where it circulates until it gets to the lungs where it is expelled in your normal breathing routine. this happens because alcohol molocules do not combine with the liquid it mixes with.
The expulsion of the evaporated alcohol through the breath permits the BAC to be accurately measured, since the percent alcohol being expelled contains the same level of alcohol that is contained in the blood. The amount of alcohol in 2,100 ml of expelled breath is exactly equivalent to the amount of alcohol in 1 ml of blood. With these equivalent measures in mind, it is possible to attain an accurate measure of the driver's intoxication, based on the figures set for legal limits. But how is the concentration of evaporated alcohol in the breath measured?
The driver exhales into the device, which then uses electrochemical fuel cell technology to identify the elements found in the sample. Some devices also make use of what is known as infrared spectrophotometer technology, which also helps to identify the presence and percentage content of alcohol in the sample.
