Breathalyser FAQs

Alcohol testing is an analysis of the amount of alcohol (ethanol) in the body. Alcohol tests look at the blood alcohol content, which is determined by a breath sample or a blood sample.

A breathalyser (also known as a breathalyzer) is a device used in alcohol testing to estimate an individual’s blood alcohol content (BAC) from a breath sample.

A breathalyser does not directly measure the blood alcohol content or concentration. This requires the analysis of a blood sample. Instead, they estimate BAC by measuring the amount of alcohol in one’s breath.

What is BAC?

BAC is short for blood alcohol content (or blood alcohol concentration or level). It is used as a metric of alcohol intoxication for legal and medical purposes.

BAC is usually expressed as a percentage of alcohol (ethanol) in the blood. It is measured in grams of alcohol per 100 millilitres (ml) of blood. For example, a BAC of 0.05 means that 0.05% of a person’s blood, by volume, is alcohol, i.e. that your body contains 50 milligrams of alcohol per 100 ml of blood.

Your BAC starts to rise as soon as you start drinking, and it can take 30 minutes up to 2 hours after you have stopped drinking for your BAC to reach its highest concentration.

The principle behind a breathalyser

The alcohol that you drink does not get digested by the body. Rather, alcohol is absorbed into your bloodstream through membranes in your mouth, throat, stomach and intestines.

After absorption, the alcohol travels in your blood and gets distributed to various tissues. One of the places that it ends up in is in your lungs, where there are tiny blood capillaries that interface with the air. In the lungs, the alcohol in your bloodstream is evaporated into the breath that you exhale.

Evaporation occurs because alcohol is a ‘volatile’ solution, meaning that its molecules do not combine with the liquid that it mixes with. Because of its votality, as your blood passes through your lungs, some of the alcohol passes over your lungs’ air sacs (alveoli), and gets released by your breath.

The percent alcohol exhaled in your breath contains the same level of alcohol that is contained in your blood. The amount of alcohol in 2,100 ml of exhaled breath is exactly equivalent to the amount of alcohol in 1ml of blood. Therefore it is possible to attain an accurate measure of your blood alcohol content from your breath.

A breathalyser measures the amount of alcohol in your lungs using your breath sample, therefore determining your blood alcohol content.

What’s in a breathalyser?

A breathalyser consists of a sampling system, a reaction chamber, and a sensor (or detector).

The sampling system collects the air that the user blows into the device and redirects it to the reaction chamber, whereas the reaction chamber contains several chemicals that retain and react with any trace of alcohol in the breath or air.

The sensor or detector is what measures the chemical reaction and processes the reading. There are two types of sensor technologies that are used to measure breath alcohol content:

1. Semiconductor Sensor

A semiconductor sensor oxidises alcohol electronically using a tin-oxide substance. It carries out a redox reaction of ethyl alcohol to acetic acid and water, and then measures the current that’s generated by this reaction. The current measured is used as an indication of how much alcohol is being reacted in the breath.

Semiconductor sensors are accurate assuming there are no interfering volatiles in the bloodstream, and assuming that breath temperature is not variable. It is recommended to wait 20 minutes after the last consumption of alcohol or food before using the unit.

Semiconductor sensors are low in cost and are commonly used in personal breathalysers and breathalysers for low-volume professional testing. These breathalysers perform very well and give accurate readings when maintained or calibrated regularly every 6 months.

2. Fuel Cell Sensor

Fuel cell sensors are one of the most advanced methods of determining a person’s BAC. It measures alcohol content by creating a chemical reaction through platinum metal that oxidises the alcohol in the sample and produces an electrical current.

Fuel cell sensors are more alcohol specific (for ethyl alcohol) and reduces false readings from substances such as ketones that are similar in chemical structure to alcohol. They are therefore more accurate and very stable, but also more expensive.

Fuel cell breathalysers are commonly used in industrial or evidential grade breathalysers such as in workplaces, medical settings, and in law enforcement. They require calibration less often, usually every year or every 1000 tests.

Choosing a breathalyser

When choosing a breathalyser, it is important to consider the following factors:

1. Test and certification by a recognised organisation

For example: SAI Global (Australian Standard), DOT (Department of Transportation), or NHSA (National Highway Traffic Safety Administration).

Most workplaces require that the breathalyser used is certified to Australian Standard AS3547, a standard that assures the accuracy, reliability, and performance of the breathalyser. For consumer use, a certification may not be as important.

Australian Standard breathalysers undergo extensive laboratory and field testing to get this certification. This also means that the breathalyser is serviceable and well supported through a strict control process as a safety device. The majority of Andatech’s industrial breathalysers have been tested for this standard.

2. Flow Sensor to capture deep lung air sample and monitor pressure.

Good quality breathalysers contain a flow sensor that requires you to blow into the device for a minimum amount of time. This is to assure that you expel enough air out of your lungs to get a ‘deep-lung’ sample where the most accurate reading can be obtained.

3. Mouthpieces for a more accurate reading.

Using mouthpieces when exhaling air into the breathalyser helps to minimise the impact of external air, therefore providing a more accurate reading. Some breathalysers have an active mode or passive mode or both. Active mode requires mouthpieces, whereas passive mode does not. Using a passive mode breathalyser without mouthpieces may be more convenient but will affect the accuracy of the readings.

4. Sensor accuracy.

Consider whether the alcohol tester has good sensor accuracy in a controlled environment.

Personal use
Most consumers use semiconductor breathalysers as these are cheaper and ideal for personal use . For a more accurate unit, consumers can choose a fuel cell breathalyser, which are more expensive but more accurate.

Workplace use
Employers looking for a breathalyser for employee testing should opt for fuel cell breathalysers, which are more accurate and stable. Fuel cell breathalysers are also ideal for high-volume testing, and many of them come with extra capabilties such as internal memory and printing.

5. Breathalyser calibration.

Breathalysers need to be calibrated regularly (usually every 6 or 12 months) to maintain its accuracy. Fuel cell breathalysers generally require calibration less often than semiconductor breathalysers. Take this into consideration when choosing a breathalyser for yourself, as sending a breathalyser back for calibration would mean potentially having to go a few weeks without a breathalyser.

Check out our infographic on how to choose a breathalyser >

Is workplace alcohol testing legal?

Yes it is, but to a certain extent.

Australian businesses and organisations are required by law to provide a safe workplace for their staff, visitors, and the wider community. In occupations where safety is critical, employers can conduct a drug and alcohol testing program as an effective risk management system to help prevent workplace accidents. Random drug and alcohol testing is considered appropriate.

Although everyone in the workplace has a role in maintaining occupational health and safety, under the Occupational Health and Safety (OHS) Act, the ultimate responsibility for providing a safe workplace rests with the employer. According to the OHS Act:

  • All employers are legally obligated to maintain a safe workplace without risks to health.
  • All employers may justifiably consider the implementation of drug and alcohol testing.
  • All workplaces in high risk areas such as manufacturing, mining or construction are especially recommended to consider the implementation of drug and alcohol testing.

Employers should also consider the Privacy Act when introducing a workplace drug and alcohol policy. Read our article on Alcohol Testing in the Workplace for more information.

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Christina Cini

Christina Cini

Christina is our very skilled Quality Assurance Manager/ Technician. With her degree in Mechatronics Engineering, she is able to apply her field of studies to her current occupation, also providing a better understanding into our more technical blog posts such as calibration, maintenance of your breathalyser, as well as sensors.


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