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Testing yourself, or testing someone else.   What's the Difference?
Personal Breathalyzers - designed for testing yourself - are cheaper... but:

● They assume the person using them wants to get the most accurate reading possible.  Certified Breathalyzers are independentaly tested and proven to prevent insufficient samples being taken.

It is assumed that they will always be used carefully and in accordance with the user manual.  Certified Breathalyzers are designed to deal with smokers, mouth alcohol, mouthwash, misuse etc.

They will "err on the side of caution" - reacting to a wider range of substances and deliberately over-reading as a precaution.  For a personal user, this is a good thing - but when testing someone else it will often lead to a false positive. Certified breathalyzers are proven to detect only alcohol and will only provide an exact reading, to within £2% (vs £20% or more for most Personal Breathalyzers!).


Below is a table of some typical differences between Certified breathalyzers designed for testing other people and lower-cost "personal" breathalysers that haven't been certified designed for use when testing yourself.  For a more detailed explanation of why you may need to use a certified breathalyzer if you are testing someone other than yourself, read our help article "Why use a Certified Breathalyzer?"
  Personal Breathalyzers Certified Breathalyzers
They are designed on the expectation that the person being tested wants the most accurate result possible.  They are familiar with the device and know how to blow (time & pressure) in order to get the most consistent readings.   The accuracy readings given by the manufacturers (see below) are usually only acheived after considerable practice. The assumption is that the person being tested may well try to provide a false result, either by giving an insufficient sample or failing to give honest answers.   The certification process assumes an unwilling and unco-operative participant yet still ensures accurate and repeatable results over a wide range of levels from very low to high.
Sampling They mostly rely on a timer, occasionally with a minimum blow pressure.  They measure alcohol from the entire  breath sample - the majority of which has not been anywhere near the blood vessels in the lung (alviolae air).   Only this "deep lung" air can give accurate & consistent results. (see "how a breathalyzer works") They have sophisticated sensors for volume, pressure, temperature and humidity to ensure an exact sample is measured.  They sample a full lung of air - around 1.5ltrs - but only measure the last 20ml, which is the deep-lung air that has been in direct contact with the blood in the lungs.
Abuse They assume the user will look after the device and not test themselves after smoking, drinking or eating.  The sensors are not able to cope with this type of abuse and will quickly degrade or fail if misused in this way. Lack of regular use will also "dry out" the sensor leading to drift or failure. The testee may well deliberately smoke or drink in an effort to provide a false reading; they have no regard at all for any damage it might do.  The Fuel Cell sensors are therefore designed to be robust enough to cope with such abuse and not fail or provide false readings.
The user knows if they've been using (say) mouthwash and would not use the breathalyser accordingly.  To protect the user, they will provide a positive result over a wider range of substances - just in case it might be alcohol. The person doing the testing has no idea whether the person tested has, or has not, been using mouthwash, gum etc. They have to be VERY specific to pass certification and will NOT display a result for anything other than ethanol.

Usually use a semi conductor or low-cost fuel cell that is rarely more accurate than to within +/- 20% when new.  Semi conductors in particular will degrade over time, particularly if mis-used.  Generally cheap and mass-produced, they are rarely individually quality-checked. Certification requires large, high quality Fuel Cell Sensors that will tolerate considerable misuse while maintaining a high degree of accuracy over long periods of time.  They are expensive to produce, and impecable quality control is an integral part of the certification process.
Accuracy Often expressed in BAC%, such as "£ 0.02% " 0.08%"  This is in fact  £ 25% of the actual reading and it gets signicantly worse away from the calibration point (usually 0.08% BAC) - as much as £ 100% at levels of around 0.02% BAC. Assuming the user to be a driver, they will therefore over-read to "err on the side of caution" - hence false positives. Standard Draeger accuracy is a maximum of  £ 1.75% of the reading value.  Typically accurate to within less than 0.001% BAC they will only give exact, accurate results and will not provide false positive readings. They will consistently reproduce their readings during repeated testing no matter what level of alchol is tested.
Recall & Printing Typically the reading is displayed for a short period and then clears,  unable to be recalled.  Occasionally they have a basic memory function but the lack of an internal time-stamp means the test cannot be proven. A wide range or recall options are available including hard copy printouts to mobile printers, dowload of data to a PC, alphanumeric input of the name  of the person tested and even GPS time-place-date stamps to prove validity.
Longevity Used 4 or 5 times a month and exactly as per the user guide, they will typically last 2-3 years. Sensor drift is the biggest issue but so long as the breathalyser is being used by the same person, they will recognise the pattern and know to have it checked or calibrated. Designed to withstand mistreatment both in handling and sampling from the rough enviroment of a police traffic unit, they will last 5-6 years as a police device and in a commercial use they should last in excess of 10 years if calibrated on schedule.

Non-certified breathalyzers can often be used as screeners in order to test more people on a very basic level, prior to testing any positives with a certified device.  This is a perfectly acceptable use of such a device and we have a range of screening kits that are designed specifically with this in mind, but any positive results obtained they MUST be backed up immediately with a certified breathalyzer (or a blood test) to ensure there is no possiblity of false accusations being made.