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How breathalyser false positives happen

Understanding breathalyser false positives

With breathalysers being a crucial instrument in measuring blood alcohol content (BAC) to ensure safety at the workplace and on the road, the occurrence of false positives could bring about significant repercussions on one’s employment and livelihood.

When a breathalyser incorrectly detects alcohol in your breath, the device will register the foreign substance as alcohol and produce an inaccurate reading. Some repercussions of breathalyser false positives include unwarranted arrests, licence disqualifications, loss of employment, and damage to one’s reputation and it can also create scepticism on the justice system as a whole.

In this blog post, we delve into the factors that can influence breathalyser accuracy and shed light on the causes of false positives. By understanding them, we will be able to minimise their occurrence and ensure results are reliable at all times.

What can cause a breathalyser false positive?

A number of factors including breathalyser calibration, mouth alcohol contamination, environmental factors and the state of the device can cause false positives. However, before we dive into how each of these factors affect breathalyser accuracy, we must first understand how these devices really work.

Breath alcohol testers work based on measuring the alcohol content in a person’s breath that involve several steps that are as follows:

  1. Breath sample collection
  2. Chemical reaction
  3. Measurement of the electrical signal produced
  4. Conversion to BAC
  5. Display of results

With these steps involved, interferences can take place in any of the steps, which could cause false readings. There are several factors that can influence the accuracy of breathalysers. Some of the key factors are explained below.


Breathalyser calibration is an important process to reset the unit’s sensor if any drift has occurred as a result of constant use. Calibration frequency may vary from one manufacturer to the next. However, Andatech breathalysers are recommended to be calibrated every six months to maintain accuracy and to extend the unit’s initial warranty to a lifetime guarantee.

LEARN MORE: Breathalyser Calibration FAQs

Mouth alcohol contamination

Breathalysers are designed to measure deep alcohol breath for an accurate analysis of one’s breath alcohol concentration (which will be later converted to blood alcohol concentration). However, residual alcohol may sometime remain in a test subject’s mouth immediately after drinking, and the subject might contaminate the breathalyser with said residual alcohol.

Andatech recommends waiting for at least 15-20 minutes after drinking before taking a breath test to avoid this issue from occurring.

Environmental factors

Temperature and humidity can impact the performance of a breathalyser. Extreme temperatures and high humidity levels can lead to the device being inaccurate. It’s important to use breathalysers within operating conditions as specified by the manufacturer.

Interference from substances

Some substances, including medication, mouthwash or chemical compounds, may interfere with breathalyser readings that, lead to false positives or negatives. It’s best practice to disclose any relevant information about medication or substances used to authorities prior to conducting an alcohol breath test.

Device quality and maintenance

The type of breathalyser (semiconductor or fuel cell) has an effect on the unit’s accuracy. Using a reliable and high-quality breathalyser from a reputable brand can lead to better, more accurate readings and overall better performance.

LEARN MORE: Breathalyser dos and don’ts

Tips to minimise false results with breathalysers

While also designed to provide accurate results, the factors discussed above can impact their accuracy. Understanding these factors and implementing preventive measures can help you obtain more reliable readings from your alcohol testers.

Once these factors have been understood, taking preventive measures can be made easier to ensure the safety of yourself and others on the road and at the workplace, helping create a safer environment for all.

Wait 15-20 minutes after drinking before testing

It’s best practice to wait 15 to 20 minutes to ensure that alcohol is properly absorbed into your bloodstream (and eventually breath) before conducting a breath alcohol test. This ensures the sample analysed is from deep lung breath and that mouth alcohol residue would have been removed.

Avoid substances that can interfere with the breath test

Prior to conducting a breath test, avoid using mouthwash, breath fresheners and other medications that contain alcohol which may interfere with breathalyser test results. Always ensure that any products that will be consumed be it medication or otherwise, are free from any alcohol.

Regularly calibrate your device

Andatech offers hassle-free calibration plans to ease the calibration process every six months. Follow the manufacturer’s recommended calibration frequency guidelines if a different supplier is used.

Conduct multiple tests

For better results, it’s always better to conduct multiple tests to ensure that your test results are accurate and consistent. Conduct these tests with the same breathalyser with a time gap between tests or use a different breathalyser if available.

Opt for fuel cell breathalysers

Fuel cell breathalysers are known to be more accurate than their semiconductor counterparts for their ability to only measure ethanol, the compound that is present in alcohol, for better results. Fuel cell breathalysers are also able to measure breath alcohol up to three decimal places, making them the undeniably better choice.


Understanding the factors that can influence the accuracy of your breath alcohol tester is crucial for obtaining reliable and accurate results. By being aware of the device’s calibration needs, avoiding external interferences and using high-quality breathalysers, we will be able to minimise the occurrence of false readings.

Remember that responsible alcohol consumption and accurate breathalyser results go hand in hand to ensure safety at all times.

Browse through Andatech’s wide range of workplace and personal breathalysers to find the right unit to suit your needs.

Andatech also offers customised alcohol and drug testing solutions to help you create and maintain a safer working environment.