Most sensible drivers stick to soft drinks ahead of any car trip. It is dangerously daft to do otherwise: hazardous for personal safety and that of others, and also risky for licence preservation. But there are also many who enjoy a drink, but aim to play safe by having just one or two, hopeful of staying safely below the legal drink-drive limit of 0.08 per cent blood-alcohol concentration (80mg of alcohol per 100 millilitres of blood) across most of the UK, or the lower limit of 0.05 per cent (50mg) in Scotland and much of mainland Europe.

Because so much depends on getting it right and not running the risk of exceeding the drink-drive limit, there has been huge growth in recent years in the sales of personal breath-test equipment. In our past two Christmas issues of Diesel Car, we have tested and compared some of the most popular personal breathalysers on the UK market, sold through High Street shops and online traders. Their prices range from a few pounds for single-use breathalysers, handy to keep in the car for a quick check on a night out, to sophisticated electronic devices with prices in the hundreds, that can be a valuable licence guardian for repeated use over the years.

There’s just one concern about such devices. How can you be sure that the readings they give will tally exactly with the roadside breath-testing equipment used by the police? Or even more crucially, with the desk-top breath-test machine you would encounter if you were incautious enough to find yourself in a police station for a follow-up confirmation of a failed roadside test.

With that in mind, it is interesting to learn that one of the leading UK suppliers of personal breathalysers, whose products retail through Halfords and Boots, amongst other outlets, uses identical equipment to the police EBT – evidential breath tester – as a reference device to check on the accuracy of the pocket breathalyser you may choose to carry yourself as a “Can I drive?” precaution.

The standard police EBT, the Draeger Alcotest 9510, is not available in the public domain. Nor would many drivers want to acquire one, at around £13,000 plus VAT, for a piece of equipment weighing 13 kilograms. That’s a grand a kilo! Most of us dearly hope we will never come up close and personal to one of these. Normally, you would only do so after blowing over the limit at the roadside, and being arrested for potential prosecution. So the first one we have ever had the chance to inspect was on a visit to the Alcosense offices in Maidenhead, where managing director Hunter Abbot was proud to demonstrate it, and explain how the company uses the same equipment that the police operate.

You may have heard the name of Hunter Abbot in another context. He is a racing driver who has competed for the past two years in the British Touring Car Championship. Behind the desk in his office is a large display cabinet full of the trophies he has won in an illustrious track career. But while his racing life is dominated by speed and thrills, in business he is dedicated to the cause of road safety and encouraging drivers to ensure that they do not get behind the wheel while unsafe to drive. He has a trophy for that, too. In 2014 he won the Brake road safety charity’s prestigious Kevin Storey Award for “outstanding commitment to road safety”.

It is well known that the police use two types of breath testers against drunk drivers: the roadside unit is what is known as a PBT – preliminary breath test. It is a semi-conductor fuel cell device, which Hunter says gives a very reliable reading: “In reality it is very accurate, but it is not allowed to be used in evidence in court.” So what follows at the police station is a second, confirmatory test on an EBT, and it is this result on which the prosecution for driving with excess alcohol is based. The standard kit used by the police is the Draeger Alcotest 9510, which works on an infrared spectrometer. This shines a light through the breath specimen to analyse it. Alcosense has several of these machines and uses them to confirm the accuracy of the hand-held testers sold to motorists keen to stay on the right side of the law.

If you have ever wondered how long it takes for alcohol to clear your system, the answer may be longer than you think. Although food consumption, gender, age, state of health and other factors all play a part in the time it takes for alcohol to pass through your body, it is typically around one hour per unit.

Of course, the safest way to ensure you are never at risk of drink-driving is not to drink any alcohol at all before getting into the driving seat. We all know that. But in the real world, there will be times when drivers may have had a drink or two and need to drive. That’s when a self-check with a personal breathalyser is a better route than taking a chance on it. Especially when you know that the reading it gives is on a par with what that that official-verdict machine at the police station will say.

Sue Baker