Frequently Asked Questions
…and other useful breathalyzer information

As the UK’s most experienced breathalyer company (we’ve been selling breathalyzers since 2002, and train the staff of some of the UK’s largest PLC’s) we are often asked similar questions about Breathalyzers – how they work, what the differences are, what the different displays mean etc.

Below we’ve gathered together some of the more typical questions which you may find useful in deciding which device is the best one for you, how it works and what you can expect from it. In all, the most complete set of Breathalyzer FAQ available anywhere on the Internet!

Where does the word “Breathalyzer” come from?

The word breathalyser was originally trade-marked by a US company better known for it’s guns — Smith & Wesson, but was later sold to European Company Dräeger and has become known as a generalized trademark for all such instruments.  In the USA it was more common to spell the word “Breathalyzer” with a “z” and this has also become more common throughout the world.

Early Breathalyzer Use

The original breathalyzer was based upon a crystal-filled tube, with a bag to ensure a correct sample was taken and was introduced into the UK by Dräeger in 1967. Several other manufacturers produced tubes without bags. However, without the bag to determine a correct sample size the results were far too unreliable for law-enforcement use. In 1979 Dräeger produced the first digital breathalyzer, allowing multiple tests to be carried out far more accurately.

Consumer breathalyzers vs police breathalysers

In recent years there has been a large number of “consumer” or “personal” breathalyzers introduced, however these devices generally make use of far cheaper semi-conductor based sensors which estimate the concentration of the sample based upon one or two pre-calibrated points, typically 0.03% and 0.10% BAC. At these values they tend to be quite accurate, but away from their datum points the drift can be quite dramatic – anything up to 30-35% variance on cheaper models is not unusual. The Semi-Conductor technology is however also dramatically cheaper; whereas a typical Police Breathalyzer costs around £800, many semi-conductor devices sell for less than £30 (although some of their claims for accuracy are at the least, questionable!)

Hand-held field testing devices are generally based on electrochemical platinum fuel cell analysis and, depending upon jurisdiction, may be used by officers in the field as a form of “field sobriety test” commonly called PBT (preliminary breath test) or PAS (preliminary alcohol screening) or as evidential devices in POA (point of arrest) testing. Digital Breath analyzers do not directly measure blood alcohol content or concentration, which requires the analysis of a blood sample. Instead, they estimate BAC indirectly by measuring the amount of alcohol in ones breath.

How does a breathalyzer Work?

When you drink, alcohol is digested in the stomach and passes through the stomach wall into the blood stream. Broadly speaking, neat alcohol (such as a straight whisky for example) drunk on an empty stomach is likely to enter the bloodstream more quickly than, say, a milk-based cocktail drunk after a fairly full meal. This does not mean you will become more intoxicated from the straight whisky – just that the effect is likely to be felt more quickly. Once in the blood stream it passes around the body and generates the usual effects of alcohol on the body and brain. As the blood passes through the liver it is gradually filtered from the bloodstream, reducing at each “pass” until there is no longer any residual alcohol in the body. It also passes through the alveoli in the lungs, and as you breathe and the oxygen passes into the bloodstream, so does some of the alcohol in your blood “evaporate” into the air in your lungs. It is this alcohol that a Breathalyser is designed to measure. This is why it is necessary to measure deep lung air when using a Breathalyzer (see “sampling” below), and why it is important not to drink within 15 minutes of testing – otherwise alcohol that remains in your mouth will be blown directly into the detector, at far higher concentrations than is the case from alcohol that has passed through the stomach, into the bloodstream, and into the air you breathe out. Clearly the concentrations are often very low and the sensors have to be very sensitive to detect the levels involved – hence why it is so important not to smoke or drink before using them and why obtaining an accurate and consistent sample of air is so important.

The chemistry of a fuel cell breathalyzer

For those with a technical interest, when the user exhales into the breathalyzer, any ethanol present in their breath is oxidized to acetic acid at the anode: CH3CH2OH(g) + H2O(l) ? CH3CO2H(l) + 4H+(aq) + 4e- At the cathode, atmospheric oxygen is reduced: O2(g) + 4H+(aq) + 4e- ? 2H2O(l). The overall reaction is the oxidation of ethanol to acetic acid and water: CH3CH2OH(l) + O2(g) ? CH3COOH(l) + H2O(l). The electrical current produced by this reaction is measured, processed, and displayed as an approximation of overall blood alcohol content by the breathalyzer.

Homeostatic variables and Partition Ratios

UK Certified Breathalyzers assume that the subject being tested has a 2300-to-1 partition ratio in converting alcohol measured in the breath to estimates of alcohol in the blood. This measure is in direct proportion to the amount of grams of alcohol to every 1 ml of blood. However, this assumed partition ratio varies from 1300:1 to 3100:1 or wider among individuals and within a given individual over time. Assuming a true blood-alcohol concentration of .07%, for example, a person with a partition ratio of 1500:1 would have a breath test reading of .10% over the legal limit. Most individuals do, in fact, have a 2300-to-1 partition ratio in accordance with William Henry’s law, which states that when the water solution of a volatile compound is brought into equilibrium with air, there is a fixed ratio between the concentration of the compound in air and its concentration in water but it is important to appreciate that this ratio is constant at a given temperature; very few “personal” breathalyzers incorporate a temperature check in their software/hardware solutions. Breath leaves the mouth at a temperature of 34 degrees Celsius. To ensure that variables such as fever and hypothermia could not be pointed out to influence the results in a way that was harmful to the accused, most instruments are calibrated at a ratio of 2300:1, underestimating by 9 percent. In order for a person running a fever to significantly overestimate, he would have to have a fever that would likely see the subject in the hospital rather than driving in the first place. Thus, a machine using a 2300-to-1 ratio could actually overestimate the BAC. As much as 14% of the population has a partition ratio above 2300, thus causing the machine to under-report the BAC.

How to use a personal breathalyzer

Personal breathalyzers are much cheaper than Certified Police devices and while they  can never replicate the absolute reliability and accuracy of the Police units  (see “Sampling Methods” and “Sensor Types” etc below) they can nevertheless be very useful when used over a period of time to generate a “picture” of how you absorb alcohol. Everyone is different, and factors such as the time taken drinking, the last time you ate and your own metabolic rate can all affect quite dramatically the rate at which alcohol is absorbed. It is impossible to simply equate 1 “unit” per hour, or any other simplistic statistic, and then guess your resulting level. A recent independent test carried out by the IOC newspaper group used one of our Breathalyzers to test a random sample of drinkers in Croydon one Saturday night, and the results showed just how wildly wrong people were in trying to guess their level of intoxication.  Using a personal Breathalyzer on a regular basis means the user can build up a broad idea of the way in which they personally react, at a time when they are not going to go anywhere near a vehicle, and can help them to make sure they do not find themselves still over the limit “the morning after the night before”!

The way to get the most from your Personal Breathalyzer is to use it regularly and use it to monitor the change in your level of intoxication, rather than looking at a single specific reading.  Always wait at least 15 minutes after drinking or smoking (or you can damage the sensor) and then test yourself, trying to blow steadily and consistently (see sampling below) so that you blow the same each time. Take 3 tests, each approximately 2 minutes apart, and compare the readings; if one is substantially different to the other two, try once more. when you have three readings that are within a reasonable difference of each other, take an average and wait 30 minutes – then test again. Don’t be surprised if the reading is not exactly the same every time – see Sampling, Sensors and Displays below) – carry on testing every 30 minutes until you get a zero reading. You may well find that the reading initially INCREASES, between the first few tests and the next – this is because it is taking time for the alcohol to be absorbed into the blood stream from your stomach. You will also probably find that the level does not drop by the same amount every half hour – this is one of the main reasons you bought your detector, to see how YOUR body reacts and how long it takes to absorb the alcohol. You can use the guide to UK limits below to get some idea of how your readings compare, but if you intend to drive – do NOT drink!

Sampling method

One of the biggest differences between Breathalysers is the way in which they sample your Breath. Professional, police-grade Breathalyzers measure an exact volume of air each time they are used – usually 1.2 litres. They incorporate a flow meter to measure the air and a physical gate to divert excess air once the required sample has been taken. This means they can obtain accurate results every time irrespective of how the user blows.

In contrast, “Personal” Breathalysers have varying methods of regulating the sample taken – some better than others! The simplest is the “Blow on” sensor – Keychain style and the compact “handbag” types all use this method, with a short sample of breath taken by blowing at the unit. The AL2500 has a vent at the top of the unit which the user blows through instead of onto but none are able to take a full sample of deep lung air, but as a result the user must expect a reasonably large margin error with such units. The next “step up” is to make the user blow through a tube; this helps to regulate the rate of sample, and enables a better standard of measurement to be taken. Further up the range breathalyzers incorporate a pressure sensor which ensures a minimum air flow is maintained during sampling (though none will limit the maximum sample that can be taken).  Next level up you have the Personal Fuel Cell devices.  These breathalyzers do use the same type of sensor as Police devices and offer a far more consistent & reliable alternative to the cheaper semi-conductor devices – without the cost of Police Approval.  When used regularly by a single individual, who develops a consistent blow of around 1.2 litres of air, the “blow-through” types can obtain a reasonably good level of accuracy, however anyone considering using a Breathalyzer to test others should be using a certified breathalyzer to be certain that the sample is identical and reliable every time.

Sensor Types

Traditionally Breathalyzers were all designed around a device called a Fuel Cell. These are relatively expensive to manufacture (often £200 or more just for the Fuel Cell) but are highly accurate and reliable over a wide range and Breathalyzers certified for evidential use (known in the US as EBT’s) use these sensors. In order to produce a more economic device for personal and home use various semi-conductor based sensors have been developed, which use varying levels of software complexity to translate their readings into equivalent values such as BAC%, mg/l and Micrograms. These sensors are more susceptible to drift (where the values produced gradually vary as the unit gets older and is used more often), saturation/contamination (for example if the user has been smoking or drinking recently) and variations in temperature but for general home use, provided some margin for error is allowed by the user, can produce some perfectly acceptable results. Semi-conductor based sensors also have a narrower range of sensitivity and are more complex to calibrate (see below) so for Employers or Enforcement agencies, who must have a reliable and consistent reading over the full range of use, only Fuel Cell, EBT-approved devices like the AlcoDigital 3000 and Dräeger 5510 are going to produce the required levels of accuracy and reliability.

Users should also bear in mind that the accuracy of a particular sensor quoted in the specifications has been measured under strict laboratory conditions immediately following calibration. Due to the variations listed above, and particularly the limitations of sampling, it is unlikely that such specific accuracy is likely to be obtained on a repeatable basis by the user “in real life” and sensor saturation with alcohol, or contamination with smoke during a test, can quickly destabilize the sensor software and lead to unreliable results. Anyone using a “personal” Breathalyzer should leave a substantial margin of error and take into account general factors such as what and when they’ve been drinking – you cannot rely solely on a Personal Alcohol Detector to determine your level of intoxication!


Many handheld breathalyzers sold to consumers use a silicon oxide sensor which are far more prone to contamination and interference from substances other than breath alcohol. The sensors require recalibration or replacement every six months. Higher end personal breathalyzers and professional-use breath alcohol testers use platinum fuel cell sensors. These too require recalibration but at less frequent intervals than semiconductor devices, usually once a year and they are far more robust when it comes to dealing with high concentrations, such as would be found (for instance) in a rehabilitation clinic. There are two methods of calibration – dry gas, and wet bath simulation and all Breathalyzers can only remain accurate for so long before they need to be “reset” – or calibrated – against a known benchmark concentration level of alcohol. Each method requires specialized equipment and factory trained technicians. It is not a procedure that can be conducted by untrained users or without the proper equipment. On the whole a personal detector will remain accurate provided it is used properly, but once consecutive readings start to drift by an unacceptable degree then it will need to be recalibrated. Regular recalibration (roughly every 6 months) also helps ensure the sensor stays within calibration range; once outside this range, it cannot be reset. Some semiconductor models are designed to allow the sensor module to be replaced without the need to send the unit to a calibration lab however as replacing the sensor does not test the unit itself “in situ” this method is not as reliable as having the unit properly serviced by a trained technician.

Fuel Cell devices will generally “hold” their accuracy for longer, however because they are usually in use in an evidential environment most companies have them calibrated at least every six months. Dry gas calibration can only be carried out on Fuel Cell devices and is generally done at a single concentration level. Fuel Cells have a much more linear detection range the semi-conductor based sensors and as such are able to “predict” accurately both lower and higher concentrations from a single calibration point. The advantage of dry gas calibration is that little or no expertise is required to operate the equipment, and large-scale operators such as the police are able to have their own in-house setup in order to regularly check and calibrate their detectors. If the readings are not what you expect, first try re-testing on several occasions to see if blowing technique is an issue – see “how to use a personal Breathalyzer” and “sampling methods” above.

Semi-conductor devices on the other hand are calibrated using wet-bath simulators, which is a device containing water, mixed with pure alcohol at a precise level and heated to an exact temperature. A minimum of two are required, and a Customs & Excise licence is required to purchase and store the materials. Semi-conductors have a much narrower, and less linear, range than fuel cells and so are usually calibrated at two points – a “low” level and “high” level just above and below the expected key point of use – in the UK, either side of the drink drive limit of 0.08 BAC%. The software in the unit then compares these two fixed points from the air supplied by the wet bath simulator and uses them to forecast other readings up and down the range. The problem however is that it is relying on the software to predict the results, and the non-linear nature of the sensor means it can only do so to within certain limits, particularly at very high (more than 0.20 BAC%) or very low (less than 0.02 BAC%) levels. For personal use, as a general indicator of changes in the level of intoxication, semi-conductor based Breathalyzers are very useful devices but users cannot put too much store by any one specific reading and must allow reasonable margin for error (see Sensor Information here). To have a Breathalyzer calibrated, see our order page here.

Displays and measurement Units – BAC%, mg/l, micrograms, etc

There are three basic types of display; LED’s that show a range of values (like the SafeDrive Keychain and CA1000) and either backlit LCD or Digital LED devices that produce a digital reading. These displays generally show three digits, however if calibrated to display the results in BAC% one digit is always a zero (The UK limit is 0.08%BAC, so even someone 5 times over the UK limit would still only register a reading of 0.40%BAC). Alternative forms of measurement include Mg/L of breath (where the limit is 0.35), mg/100ml blood (where the limit is 80mg – this is the measurement reference used by UK police until around 5 years ago) and Micrograms per 100ml breath (the current Police standard, where the UK limit is 35 micrograms)- bit confusing? we agree.

Most “Personal” Breathalyzers sold in the UK display their results in BAC%, which is the standard most commonly used in the US. The problem with this standard is that between zero and the drink-drive limit of 0.08, the unit only displays a change of 8 “steps” of 0.01%, and approximates the values in between. For example, 3 tests taken 2 minutes apart may produce sensor values of 0.045, 0.050, and 0.055 – but all would display as 0.05. On a unit displaying mg/100ml however, the full reading would be displayed in full as 045, 050 and 055 allowing the user to make a more informed decision. Bearing in mind the comments made above with regard to sampling, it also gives the user more feedback as to the consistency with which they are using the Breathalyzer.

Certain websites claim that their devices actually “read” a sample in BrAC – “Breath Alcohol Content”. Clearly this is nonsense – every sensor merely outputs an electrical signal, which is then converted by the software in the unit to correspond to an accepted value of measurement. Whether that is BAC%, mg/L, mg/100ml or Micrograms is irrelevant – different standards have been adopted by different countries and all are as valid as each other provided the device is used correctly and properly calibrated at the time. It is the same as weighing an apple in grams, pounds, kilos, stones etc – the apple still weighs the same!

UK & USA Breathalyzer Approval Standards, ASD’s vs EBT’s

In the UK, the Home Office ONLY approve devices for Police and Law Enforcement use and as yet only Fuel Cell, fixed-volume sampling devices like the 6510 have so far been approved. While a minimum standard for Personal Breathalyzers would be highly desirable at the moment nothing exists and as a result many low cost devices sold on the UK market are little more than novelty items.

US FDA 510k clearance

All breath alcohol testers sold to consumers in the United States are required to be certified by the Food and Drug Administration,[7] while those used by law enforcement must be approved by the Department of Transportation’s National Highway Traffic Safety Administration. Manufacturers of over-the-counter consumer breathalyzers must submit an FDA 510(k) Premarket Clearance to demonstrate that the device to be marketed is at least as safe and effective, that is, substantially equivalent, to a legally marketed device (21 CFR 807.92(a) (3)) that is not subject to Premarket Approval (PMA). Submitters must compare their device to one or more similar legally marketed devices and make and support their substantial equivalency claims. It is important to appreciate however that the FDA Screening Tests do not test the ACCURACY of the device in ANY WAY WHATSOEVER – they only check to make sure they are “capable of detecting alcohol”. And that doesn’t mean they won’t detect other substances, and report them as alcohol! The devices are cleared as “screeners” which means they have met the requirements used by the FDA for detecting the presence of alcohol in the breath, however Screener certification does not mean that the device can measure breath alcohol content accurately. Many breathalyzers cleared by the FDA are very inaccurate when it comes to BAC measurement and no semiconductor device has ever been approved for evidential use (see below) by any State Law Enforcement Agencies or the U.S. Department of Transportation. For personal use, certification does at least ensure a basic level of performance and as a pre-screener, backed up by an evidential-level tester, they certainly have a place in the workplace or clinical areas but their “results” must be treated with the scepticism applicable to a far cheaper device than a professional quality breathalyzer.

US DoT breathalyzer clearance

Department of Transportation (DoT) approve two types – ASD’s (Alcohol Screening Devices) and EBT’s (Evidential Breath Testers). Again, only Fuel Cell devices have been approved in the US as EBT’s, but there are a substantial number of semi-conductor based devices that have been approved as ASD’s, including the AlcoDigital AL6000 & AlcoDigital AL7000 etc. Users must remember that the US DoT approval is only limited to their ability to detect the PRESENCE of alcohol. They are NOT assessed for their ability to accurately measure a specific alcohol LEVEL, in the way that an EBT is. They are expected to be used only for general screening, with anyone that indicates anything over zero being re-tested using a properly approved EBT. This makes them a very useful “morning after” device for home use and for measuring the comparative rate that an individuals’ body metabolites the alcohol but users must realize that something costing in the region of £50 – £100 is not going to reproduce the level of specific accuracy and reliability of an EBT costing £700 or more.

Limitations of Personal Breathalyzers

All “personal” breathalyzers (ie. those based around semi-conductor sensors) are either non-approved, or at most approved in the USA as Alcohol Screening Devices (ASD’s) and as such the US DoT that approves them advises “The exact alcohol content in the blood of the test subject cannot exactly be determined by using an Alcohol Screening Device. Only an Evidential Breath Tester or Blood test can be relied upon for accurate determination. Do not Drink and Drive”. In addition, the following limitations must be considered:

  • The result can be affected by variations in blow technique & temperature.
  • The unit’s calibration can only be certified when issued; it cannot be guaranteed over time and can become contaminated by a single use involving smoke or excessive mouth alcohol (saturation).
  • The test reflects only the levels detected at a single point in time and levels of intoxication will often peak sometime AFTER the last drink.
  • Regular use of the detector over a period time (see “how to use a personal Breathalyzer”) is the best way to use a Breathalyzer and learn how alcohol affects the individual person. This can then be used, along with a suitable safety margin, to help ensure the user is clear of alcohol before undertaking critical tasks or driving.
  • Personal Breathalyzers can only be used to give an indication of the possible presence of alcohol in the blood. The user must NOT rely solely upon the indications provided by this equipment and must use his/her own judgment, taking all factors into account, to determine whether it is safe and/or legal to operate a vehicle.
  • Various substances can interfere with the result if not known to the person carrying out the test – see Common sources of Breathalyzer errors and False Positives below.

UK Drink Drive Limits

The legal limit for alcohol levels in the body while in control of a vehicle vary from country to country and use several different units of measurement (micrograms, mg/L etc) – but in the same way as inches and centimetres are simply different units to measure length, so these are different ways to express the same thing in terms of Alcohol in the blood or breath.

The limits below apply to England and Wales – and are the highest in Europe (In December 2014 Scotland reduced it’s limit to that of most of Europe – 50mg/l).  Reading under this limit does not mean you are not impaired – the only safe limit is Zero – and many believe (including us) that a limit of 35 micrograms is far too high to be driving a vehicle on the road. (The new Scottish limits are shown below in brackets)

  • 35 (22) micrograms/100ml breath – as used by professional Breathalyzers such as the AlcoDigital 3000 and all UK Police Breathalyzers
  • 80 (50) mg/100ml blood – as displayed by the AlcoHawk Pro
  • 0.35 (0.22) mg/L of breath – as displayed on the AlcoDigital Platinum Lite
  • 0.08% (0.05%) BAC – used by lower priced Breathalysers such as the AlcoDigital AL2500

For those involved in the transportation industry, much stricter limits apply (for full details see here) but in principle aircrew, maritime and railway employees are all subject to a limit that is just one quarter of the above, ie:

Below is two maps of Europe showing the various limits that apply (the only other country to have a limit of 35 is Luxembourg). The first is for Private motorist and the second for novice and commercial vehicle drivers.

Drink drive limits Europe

Police drink driving limits for private motorists in Europe

Novice drivers drink drive limits Europe

Commercial and Novice drink drive limits in Europe

Mouth alcohol

One of the most common causes of falsely high breathalyzer readings is the existence of mouth alcohol. In analyzing a subject’s breath sample, the breathalyzer’s internal computer is making the assumption that the alcohol in the breath sample came from alveolar air that is, air exhaled from deep within the lungs. However, alcohol may have come from the mouth, throat or stomach for a number of reasons. So called blow over or passive testing devices are extremely susceptible to these issues, and to all intents and purposes are of little more than novelty use as a result. To help guard against mouth-alcohol contamination, certified breath-test operators are trained to observe a test subject carefully for at least 15-20 minutes before administering the test and all professional breathalyzers require the user to blow throw a tube or mouthpiece to produce a specific sample size of air from which the concentration is devolved.

The problem with mouth alcohol being analyzed by the breathalyzer is that it was not absorbed through the stomach and intestines and passed through the blood to the lungs. In other words, the machine’s computer is mistakenly applying the partition ratio (see above) and multiplying the result. Consequently, a very tiny amount of alcohol from the mouth, throat or stomach can have a significant impact on the breath-alcohol reading. Other than recent drinking, the most common source of mouth alcohol is from belching or burping. This causes the liquids and/or gases from the stomach including any alcohol to rise up into the soft tissue of the oesophagus and oral cavity, where it will stay until it has dissipated. For this reason, police officers are supposed to keep a DUI suspect under observation for at least 15 minutes prior to administering a breath test. The only approved instrument currently available that is certified to detect mouth alcohol is the Draeger 7510, released in 2010.

Mouth alcohol can also be created in other ways. Dentures, for example, will trap alcohol. Periodontal disease can also create pockets in the gums which will contain the alcohol for longer periods. Also known to produce false results due to residual alcohol in the mouth is passionate kissing with an intoxicated person. Recent use of mouthwash or breath freshener possibly to disguise the smell of alcohol when being pulled over by police contain fairly high levels of alcohol.

Common sources of Breathalyzer errors and False Positives

The temperature of the subject is also very important due to Homeostatic Variables – see below. Breath testers can be very sensitive to temperature, for example, and will give false readings if not adjusted or recalibrated to account for ambient or surrounding air temperatures. Breathing pattern can also significantly affect breath test results. One study found that the BAC readings of subjects decreased 11-14% after running up one flight of stairs and 22-25% after doing so twice. Another study found a 15% decrease in BAC readings after vigorous exercise or hyperventilation. Hyperventilation for 20 seconds has been shown to lower the reading by approximately 32%. On the other hand, holding one’s breath for 30 seconds can increase the breath test result by about 28%. The National Highway Traffic Safety Administration (NHTSA) also found that dieters and diabetics may have acetone levels hundreds or even thousand of times higher than those in others. Acetone is one of the many substances that can be falsely identified as ethyl alcohol by some breath machines. However, fuel cell based systems are non-responsive to substances like acetone. A study in Spain showed that metered-dose inhalers (MDIs) used in asthma treatment are also a cause of false positives in breath machines. In general Evidential Testers such as the Draeger 6810 are highly resisitve to such issues as they are specifically designed for testing an “unwilling” subject – this is why a personal, semi-conductor type tester should never be used for testing anyone other than the owner, who is well aware of anything they may have taken that could affect the result.

Products that interfere with Breathalyzer Testing

Products such as mouthwash or breath spray can “fool” breath machines by significantly raising test results. Listerine mouthwash, for example, contains 27% alcohol. The breath machine is calibrated with the assumption that the alcohol is coming from alcohol in the blood diffusing into the lung rather than directly from the mouth, so it applies a partition ratio of 2100:1 in computing blood alcohol concentration resulting in a false high test reading. To counter this, officers are not supposed to administer a PBT for 15 minutes after the subject eats, vomits, or puts anything in their mouth. In addition, most instruments require that the individual be tested twice at least two minutes apart. Mouthwash or other mouth alcohol will have somewhat dissipated after two minutes and cause the second reading to disagree with the first, requiring a retest.

Popular Breathalyzer Myths

A 2003 episode of the popular science television show MythBusters tested a number of methods that supposedly allow a person to fool a breathalyzer test. The methods tested included breath mints, onions, denture cream, mouthwash, pennies and batteries; all of these methods proved ineffective. The show noted that using items such as breath mints, onions, denture cream and mouthwash to cover the smell of alcohol may fool a person, but, since they will not actually reduce a person’s BAC, there will be no effect on a breathalyzer test regardless of the quantity used. Pennies supposedly produce a chemical reaction, while batteries supposedly create an electrical charge, yet neither of these methods affected the breathalyzer results.

The Mythbusters episode also pointed out another complication: It would be necessary to insert the item into one’s mouth (e.g. eat an onion, rinse with mouthwash, conceal a battery), take the breath test, and then possibly remove the item Ñ all of which would have to be accomplished discreetly enough to avoid alerting the police officers administering the test (who would obviously become very suspicious if they noticed that a person was inserting items into their mouth prior to taking a breath test). It would likely be very difficult, especially for someone in an intoxicated state, to be able to accomplish such a feat! In addition, the show noted that breath tests are often verified with blood tests (which are more accurate) and that even if a person somehow managed to fool a breath test, a blood test would certainly confirm a person’s guilt. However, it is not clear why a negative breath test would be verified by a subsequent blood test.

Other substances that might reduce the BAC reading include a bag of activated charcoal concealed in the mouth (to absorb alcohol vapour), an oxidizing gas (such as N2O, Cl2, O3, etc.) that would fool a fuel cell type detector, or an organic interferon to fool an infrared absorption detector. A 2007 episode of the Spike network’s show Manswers showed some of the more common and not-so-common ways of attempts to beat the breathalyzer, none of which work. Test 1 was to suck on a copper coin. (Actually, copper coins are now generally often only copper-coated and mostly zinc or steel. Test 2 was to hold a battery on the tongue. Test 3 was to chew gum. None of these tests showed a “pass” reading if the subject had consumed alcohol.

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