Breath alcohol testing is an important practice carried out randomly at roadside checkpoints and also regularly at the workplace to make sure that individuals do not drive or work under the influence. The simple act of blowing into a breathalyser to measure one’s breath alcohol concentration can be explained by a series of processes.
How does alcohol end up in your breath?
Alcohol ends up in your breath once it enters your bloodstream and makes it way through your body. After a thorough process, alcohol leaves the bloodstream at the alveoli together with carbon dioxide and other gases when exhaled.
When alcoholic drinks are consumed, the alcohol compounds can be directly absorbed into the stomach lining and small intestine, entering the bloodstream. As blood circulates throughout the body, some alcohol compounds can end up in sweat, urine, and breath before reaching the liver. Once these volatile alcohol compounds reach the lungs, they leave the bloodstream at the alveoli together with carbon dioxide and other gases when exhaled.
The concentration of alcohol in exhaled air is affected by the amount of alcohol consumed, as well as the alcohol absorption and metabolic rates of an individual.
To obtain an accurate measurement of alcohol concentration in the human body, breathalysers should only measure the alcohol concentration in the deep lung air.
How does a fuel cell breathalyser work?
The fuel cell sensor of a breathalyser consists of two platinum electrodes with an acidic solution containing electrolytes in between. The breath alcohol testing process starts by having the individual blow slowly and steadily into the breathalyser through a mouthpiece or a sampling cup. The subsequent chains of events that happen when the exhaled air reaches the sensor can be summarised in 2 steps:
- Alcohol compounds, specifically ethanol compounds, are oxidised on the platinum surface, generating electrons that flow through the circuit as electric current.
- This electric current is measured by a meter in the circuit and is ‘translated’ into a breath alcohol concentration reading.
The more alcohol compounds present in the breath sample, the more electrons are produced during oxidation which leads to a higher electric current and in turn, a higher breath alcohol concentration reading.
How does a semiconductor breathalyser work?
Semiconductor breathalysers possess a tiny chip within the unit made of semiconductor material that reacts to alcohol. The breath sample deposited into the breathalyser will make contact with the sensor and cause a chemical reaction that generates an electrical signal.
The higher the alcohol content in your breath, the stronger the electrical signal gets.
Once the breathalyser reads this electrical signal, it converts it into a readable BAC level and displays it on the screen, similar to fuel cell technology.
The difference between semiconductor and fuel cell breathalysers is that semiconductors are more sensitive to foreign substances other than alcohol like mouthwash and other alcohol based products. Fuel cell breathalysers from Andatech are designed to only detect ethanol, the alcoholic element present in alcoholic beverages.
LEARN MORE: Semiconductor vs fuel cell breathalysers
How is alcohol calculated in the breath?
In Australia, the two units of measurement commonly used in breath alcohol testing are %BAC and g/210L, which represent the percentage of blood alcohol concentration and the weight of alcohol in grams per 210 litres respectively.
%BAC for blood alcohol concentration
As it is not possible to obtain the actual blood alcohol concentration of an individual without conducting a blood test, a breathalyser displays the blood alcohol content reading in %BAC (also known as g/100mL) by converting the breath alcohol concentration measured based on the blood to breath ratio of 2,100:1 before displaying the reading on the breathalyser. This calculation is done based on the assumption that 1 part of alcohol in the exhaled air is equivalent to 2,100 parts in blood.
In Australia, the legal limit of blood alcohol concentration is below 0.05%BAC when driving and 0 for individuals with a learner or a provisional license. Companies can determine their own blood alcohol concentration limit for employees in their alcohol and drug testing policy to create and maintain a safe working environment.
g/210L for breath alcohol concentration (BrAC)
While %BAC is the unit of measurement more commonly used for the general public, the breath alcohol concentration displayed in g/210L is usually used in industrial settings. Breathalysers set to measure in g/210L do not convert breath alcohol concentration to blood alcohol concentration; the breath alcohol test results are measured and displayed as they are.
All breathalysers certified under the latest Australian Standard AS3547:2019 are required to use g/210L as the unit of measurement.
Can breathalysers produce false positives?
Breathalysers can produce false positive readings when the unit mistakens other substances in the exhaled air for alcohol. Some substances have These substances have a similar chemical structure to alcohol compounds and could react with a breathalyser sensor.
Below are some common compounds that could affect a breathalyser reading:
Ketones and acetones
They are produced in the human body during ketosis where fats are burned instead of glucose. Ketosis can happen when an individual is on a low-calorie or keto diet, or in diabetic individuals.
Alcohol residue in the mouth
Even though alcohol evaporates quickly, when a breath alcohol test is conducted right after alcohol is consumed or mouthwash containing alcohol is used, the alcohol residue from the mouth can be mistaken as alcohol content in deep lung air.
Hand sanitiser, perfume, paint, etc.
Alcohol-based products, such as hand sanitiser and perfumes, have volatile particles that can get into the breathalyser by chance, subsequently affecting breath alcohol test readings.
LEARN MORE: How breathalyser false positives happen
Nevertheless, fuel cell sensors are more capable of providing an accurate breath alcohol concentration reading without being affected by interfering substances in general, compared to semiconductor sensors used in older breathalyser models. Breathalysers certified under AS3547:2019 are tested extensively to ensure their reliability in various environmental conditions, including the presence of interfering chemical compounds.
Even though the concentration of alcohol in an individual can be measured through other means, such as blood or urine testing, using a quality breathalyser is the most convenient method that can be done anytime, anywhere.
A handheld breathalyser is suitable for ad hoc breath alcohol screening in the workplace while a wall mounted breathalyser installed on-site is fitting for regular breath alcohol testing as employees clock in for work. Choosing a suitable breathalyser is essential for the smooth implementation of your company’s alcohol and drug testing policy.
Browse through Andatech's selection of personal breathalysers for everyday alcohol safety or workplace breathalysers for advanced safety at the workplace to find the right breathalyser to suit your needs and help create a safer environment for all to enjoy.
Disclaimer: The information provided in this article is for general reference only. Please seek advice from professionals according to your business’s needs.
Written by Jaka Exstrada