Breathalysers are used by many as a tool for estimating our blood alcohol content (BAC), but a common yet important question that is often raised about breathalysers is – how accurate are they? We address some of the common misconceptions that consumers have about breathalysers, and share with you some information on breathalyser accuracy.

1. Breathalysers test for BAC indirectly.

A breathalyser works by measuring the BAC in your breath by taking a deep lung air sample. As alcohol is actually absorbed into the blood stream, a blood test would actually be much more accurate and reliable than a breathalyser test, but blood tests are also more costly in terms of time and resources.

In saying that, a breathalyser actually measures your BAC indirectly, and though it may not be as accurate as a blood test, a breathalyser is still the best tool to estimate for BAC as it is more convenient to transport, easier to administer and provides faster results. Breath tests are still accepted as accurate and reliable tools of measurement for use in drink driving investigations, if administered correctly.

2. The type of breathalyser sensor makes a difference.

There are two major types of sensors used in breathalysers – semiconductor sensors and fuel cell sensors. Semiconductor sensors are less expensive and therefore more widely used in breathalysers targeted at consumers, but they are also less accurate. Fuel cell sensors are more expensive and are used mostly by the police force and by companies for workplace drug and alcohol testing.

Semiconductor sensors are less stable over time and require calibration more frequently, after about 200 tests or every 6 months. They also have a lower accuracy range, about +/- 0.01%BAC. This means that if the breathalyser shows a reading of 0.03, the real BAC level is estimated to be between 0.02 to 0.04 %BAC.

On the other hand, fuel cell sensors are more stable over time, requires calibration less frequently (every 500 tests or more, or every 6 months) and provides a more accurate reading, at an accuracy range of about +/- 0.005%BAC. So, a given reading of 0.030 would mean that the BAC level is estimated to be between 0.025 to 0.035 % BAC.

3. Breathalyser maintenance is important.

All breathalysers need to be calibrated regularly, either every 6 months or 12 months, depending on the unit itself. A breathalyser that hasn’t been calibrated will provide inaccurate readings.

Breathalysers that haven’t been used for a long period of time will also provide inaccurate readings.For example, all our breathalysers are calibrated before dispatch, but if you keep it and use it for the first time only after 4 months, it would be inaccurate and would need to be calibrated again.

4. User errors occur.

Breathalysers that are not used correctly will not provide accurate readings.

Using a breathalyser immediately after taking a drink can provide a higher BAC result, and also damage the sensor. The residual alcohol in the mouth takes roughly 20-30 minutes to dissipate, which is why we always advise users to wait at least 20 minutes after consuming anything before taking a breath test.

Using a breathalyser without the mouthpiece will also damage the sensor. The mouthpieces are designed to filter out spit and moisture from the breath sample, because moisture can damage the breathalyser’s internal sensor.

5. Different individuals reacts to alcohol differently.

As long as a breathalyser is maintained properly and used correctly, it will provide you with a good estimation of your BAC.

Many users think that a breathalyser is incorrect because it shows a lower reading than expected because he/she definitely does not feel fine after having more than a couple of standard drinks.

The fact is that everyone reacts to alcohol differently. Even at low concentrations of alcohol, such as .02%BAC, one can feel very dizzy and confused. Our BAC level will differ based on the number and type of drinks we’ve had, our gender, body size, weight and prior food and drink consumption.

If you’re buying a breathalyser, here are some things to consider in terms of accuracy:

  • If you want a breathalyser for personal use just to keep yourself in check on the weekend, a semiconductor breathalyser should be sufficient for your needs. It may not be as accurate but it will give you a good estimation of your BAC.
  • If accuracy is very important to you, or if you are buying for workplace alcohol testing, then a fuel cell breathalyser would be much more ideal, though more expensive.
  • Accuracy needs to be maintained through regular calibration and proper usage.
  • Keep in mind that everyone reacts to alcohol differently, so a different BAC reading may not necessarily mean that it is inaccurate.
We recommend that you never get behind the wheel with any alcohol in your system, even if your breathalyser reading shows that you are below the legal limit. Alcohol affects your judgement and coordination, in even in small concentrations.