Can you trust personal breathalysers?

CHOICE trialled electronic and disposable breathalysers and the results were disturbing.
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04.Usability of the devices

Breathalysers group shot

The tested breathalysers.


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The trialists assessed the ease of use of each device according to how easy it was to follow instructions, prepare the device and read the results.

They found most of the electronic breathalysers easy to use. This type is reusable, with many resembling mobile phones. Generally, all that’s required is to press a button on the device, wait until prompted, blow into the mouthpiece for a few seconds and the reading appears.

The FiT 208-S, which claims to be user-friendly, rated lowest for ease of use. Our trialists found its operating instructions “too complex”. Interpreting its readings was also confusing — the BAC levels in the instructions are stated as a range of percentages that require conversion.

Another downside is if your reading is below 0.015, the device only indicates “Lo”. Similarly, trialists found the Digitech’s instruction leaflet hard to understand. This model also delivered too many underestimates (see table). The Alcosense Mini has easy-to-follow instructions and is the only electronic breathalyser that does not require a mouthpiece, but it delivered poor accuracy results.

Disposables hard to use

The two disposable models on trial, BreathScan and Redline, are about half the length of a pen and consist of chemical crystals within a glass tube. The crystals in both react to alcohol fumes and change colour when they’re over 0.05. Our trialists rated both poorly for ease of use, just as they did in 2005.

BreathScan requires you to break the seal and blow hard into the tube for 12 seconds. If you’re over the limit, the crystals change from yellow to a pale bluish-green. But this was not always obvious to our trialists.

The colour change in the Redline from yellow to green was much more obvious than in the BreathScan, however, many trialists still found it hard to interpret the readings. The colour change progresses along the tube and if it stayed on the red line, trialists could not understand what the reading meant. When the colour change crosses the red line, it means the trialist’s BAC is above the 0.05 limit. Conversely, when the colour change stays below the red line, it means the BAC is under 0.05.

The Redline is also cumbersome to prepare. To use it you must break off the ends of the glass tube, attach a plastic bag, blow into it to inflate it, then squeeze the air through the tube to obtain a reading — a feat that would be difficult to manage discreetly in a pub.