With a Semi Conductor Breathalyzer, while the
sensor is generally quite accurate around the two calibration points of 0.03%
BAC and 0.10% BAC (UK limit 0.08%) the results can be less satisfactory outside
of these ranges, and particularly so at lower levels below 0.03%. Needless
to say, manufacturers all quote their accuracy as a figure +/- (x)% at the 0.10%
level, and while this is generally repeated at this level accuracy does diminish
at other measuring points.
A Fuel Cell, on the other hand, measures
evenly throughout the range, hence why they are the only types of sensor used
for Police grade detectors. Fortunately, while a Police standard detector
(such as the Dräeger 6510) costs around £700 there are now several Fuel-Cell
based Breathalyzers available at considerably less - the AlcoHit Pro for
instance is just £199.
The other reason for the price difference is
generally down to the sampling method. To get an accurate reading you need
an accurate and consistent sample, but whereas the Fuel-Cell type of
Breathalyzers also measure exactly 1.7ltrs of air each time (and expel the
remainder through an air valve) the semi conductor models use either time alone
(say a 3 second blow) or combination of time and pressure.
Because the levels tested within these
industries are so low (just a quarter of the UK Drink-Drive limit) and the
consequences so severe (in many cases the loss of an entire career, not just a
job with a particular company) it is vital that an accurate and reliable device
is used. In principle, while expensive, we would have to recommend the Dräeger
6510 as THE best device for the job, as it is exactly the same as the detector
that would be used should you be unfortunate enough to find yourself in that
situation. They are not cheap, but the ARE the best, TOTALLY reliable and
by far the most accurate devices available. Considering what is often at
stake, it may well be worth the cost, however there are now at least two other
fuel-cell base devices available at much lower cost which may suffice.
