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OK, so it sounds obvious – blow into it, wait for the results, right?  But there are some things you can do with your new purchase to make sure the results you are getting are results you SHOULD be getting.

Most people don’t realise how easily swayed some of the cheaper semi-conductor units are.  They don’t have the capacity to measure a fixed volume of air (unlike the more expensive fuel cell devices), so get round the problem by using a sensor that is activated for a fixed period of time, for example, 5 seconds.  It then generates a reading based on the assumption that the sample has produced a minimum of 1.7 litres of air.

Some of the more advanced semi-conductor units incorporate a blow pressure sensor to ensure that there actually is sufficient air passing through the device to generate a reading; cheaper ones don’t.  As a benchmark, anything costing less than £50 is unlikely to have the facility to detect whether a blow sample has produced an adequate quantity.

In any case, there are several ideals for testing:

  1. Wait at least 15 minutes after your last drink – or all you’ll be testing is the strength of alcohol residue in your mouth.  Not to mention possibly damaging the highly sensitive silicon oxide semi-conductor sensor.
  2. Perform at least 3 tests, then take the average reading.  If for example you are using the AlcoHawk Slim 2 which reads in %BAC – readings of 0.05, 0.06 and 0.04 would average out at 0.05.  Over half the UK Limit (and the point in Europe at which you would lose your licence).  Whilst a reading of this level would technically NOT be over the current UK limit, your reactions will certainly be impaired.  Not the best time to be getting behind the wheel.
  3. Wait again – an hour this time – and perform another 3 tests.  Your readings can and will continue to rise dependent on the type of alcohol consumed for anything up to a couple of hours after your last drink.  That 0.05% average could easily be 0.08% 60 minutes later.  If so, wait another hour and try again.  Eventually (or rapidly – dependent on your metabolism) the results will start to fall.  The aim of the breathalyzer is to educate yourself as to how quickly it take for you to get back down to ZERO.

Many years ago we produced a Personal Test Sheet for our customers to use when first trying out their breathalyzer.  After a few practice runs, most people become accustomed to what their limits are and what readings to expect, but when you first start out you simply cannot know.

Once you know what sort of readings you produce, with regular use you will then be able to recognise when you start getting readings that fall outside that – indicating that your unit needs to be calibrated.  But that’s whole other post.


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