So just how accurate are personal breathalyzers? - AlcoDigital

In an industry dominated by the stamp ‘Made in Korea’ the accuracy of the devices out there can vary dramatically. 

There are some wildly unrealistic claims made of units retailing at about £60 being ‘as accurate as those used by law enforcement’ (although such claims are never supported).  It would be hoped that common sense of the purchaser prevails and the expectation of a cheap key-ring matching the accuracy of, say, the Home Office Approved devices (that start at £649 plus VAT) being highly unrealistic, but unfortunately the majority of purchasers will over-estimate the accuracy they expect to receive from their breathalyzer of choice.

All breathalyzers come with a quoted manufacturer’s accuracy.  Generally this is defined as being the percentage of variation that can be expected when tested at the Calibration point of the device.  Most are calibrated at the equivalent of the UK Drink Drive limit (although some have lower or higher ‘set’ points) and as a rule, the price of the device will give some indication of the quoted accuracy.  Something to bear in mind is that the ‘quoted accuracy’ is taken from the results of procedures performed under laboratory conditions with certified calibration equipment, an environment which is virtually impossible for the average personal user to re-create. 

For the devices retailing under the £25 mark, you get pretty much what you would expect – a cheap plastic throwaway device, that will if you are lucky give you some indication of the presence of alcohol.  Just don’t expect an actual reading.  There is a reason why these devices are given away as freebies at corporate events (or with the purchase of a more expensive device), and that’s because they’re cheap.  Chances are, if you have been drinking and believe you need to test yourself to establish whether or not to drive, these devices will NOT be of assistance.

Breathalysers in the £40-£80 range generally will have an accuracy variation of about a quarter of the drink drive limit – something to bear in mind, a reading of 0.08%BAC (the UK drink drive level) could ACTUALLY be 0.06 or 0.10 – and thats when the unit is tested ‘under laboratory conditions’.

From about £100 up you would hope for an accuracy of plus or minus 0.01% variation (i.e. one eighth of the UK drink drive limit) – but again, without regular calibration this is likely to slip pretty quickly.  This is not such a problem if the user is familiar with the device and uses it regularly, and can therefore tell when he is starting to get readings that seem out of line with the usual expectations.  The danger is when these devices are used to test other people (in a Company environment, or worse still, as Medical Screening) – the personal use devices are sold as such because they simply cannot take the variations of use in a professional environment.  But that’s a whole other post…

The fuel cell devices (which start at about £150) will tend to have a much higher level of accuracy, although again quoted accuracy and actual accuracy do not always seem to match.  From £300 you are venturing into the more professional side of the industry, and generally these do actually live up to their claims although in our personal experience nothing can beat the accuracy of the Home Office Approved Draeger devices (7 years of sales with less than 0.01% fault rate – if only cars were so reliable!).

If in doubt about the accuracy, ask.  We can give you the quoted best efforts, but also tell you how that measures up in reality.  We have hundreds of units in for calibration every month, and there are certain devices which come back time and again for not living up to the manufacturers’ claims.   Ask us, and we’ll tell you which!

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