Breathalyser test finds DIY kit results worryingly erratic

Drivers could risk losing their licences plus further penalties by relying on personal breathalysers to ensure they are safe to drive after drinking.

A test by Auto Express, as part of our No Drink, No Doubt campaign, found that DIY kits can be inconsistent. We tested four, including a police-certified kit, using a gold standard calibration that mixes water and ethanol to create a sample on the cusp of the legal limit.

The police-certified Drager device gave a blood-alcohol reading of 0.076 per cent. The legal limit is 0.08 per cent, and if this had been at the roadside, it’s likely we’d have been asked to give an evidential sample.

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The cheaper devices were tested in the same way, but all recorded us as over the limit. This may seem like they’re just being safe – which is great – but in reality they returned such varied and confusing results (right) that they left us unsure of their accuracy. 

Hunter Abbott, managing director for Now Group UK, which manufactures AlcoSense breathalysers, said: “You get what you pay for with these devices. It’s hard to have any confidence in them when you get such inconsistent results.”

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A spokesman for the Association of Chief Police Officers told us: “While personal breathalysers may offer an indication of a person’s alcohol level, they shouldn’t be relied upon and would not provide any defence in court if the reading was not accurate.”

DIY Breathalyser kit test: the results

Drager 6510 Tester

6

Gave a reading of just under the limit. All three tests we ran were within 0.003% of each other. Approved by the Home Office and police-certified.

Maplin gadget tester

6

Available in Tesco and electrical stores for just £4.99. The traffic light system said we were over, but did the same for a test without alcohol.

Digital display tester

6

Provided a higher reading on one test, then gave a different result without a sufficient amount of air in it. It did the same without us blowing into it, too.

Drive Safely Tester

6

Read 0.05% for one test – its highest rewethersult – although it sometimes went green to say we were fine. Unreliable when tested without alcohol, too.

Have you ever used a DIY breath tester to check if you're safe to drive? What do you think of our test results? Let us know in the comments section below...