A
breathalyzer or
breathalyser (U.K.) (a portmanteau of
breath and
analyzer/analyser) is a device for estimating
blood alcohol contentBlood alcohol content , also called blood alcohol concentration, blood ethanol concentration, or blood alcohol level is most commonly used as a metric of alcohol intoxication for legal or medical purposes....
(BAC) from a breath sample.
Breathalyzer is the brand name of a series of models made by one manufacturer of these instruments (originally Smith and Wesson, later sold to National Draeger), but has become a
genericized trademarkA genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
for all such instruments. In Canada, a preliminary non-evidentiary screening device can be approved by Parliament as an
approved screening deviceAn approved screening device is a device used to measure the blood alcohol level of a suspected drunk driver. It is defined in the Criminal Code of Canada as: approved screening device means a device of a kind that is designed to ascertain the presence of alcohol in the blood of a person and that...
, and an evidentiary breath instrument can be similarly designated as an
approved instrumentThe expression approved instrument is a Canadian term defined in the Criminal Code of Canada as: approved instrument means an instrument of a kind that is designed to receive and make an analysis of a sample of the breath of a person in order to measure the concentration of alcohol in the blood of...
. The U.S. National Highway Traffic Safety Administration maintains a Conforming Products List of breath alcohol devices approved for evidentiary use, as well as for preliminary screening use.
Origins
A 1927 paper produced by Emil Bogen, who collected air in a football bladder and then tested this air for traces of alcohol, discovered that the alcohol content of 2 litres of expired air was a little greater than that of 1 cc of urine. However, research into the possibilities of using breath to test for alcohol in a person's body dates as far back as 1874, when Anstie made the observation that small amounts of alcohol were excreted in breath.
Also, in 1927 a Chicago, IL corner-chemists by the name of W.D. McNalley invented a breathalizer in which the breath moving through chemicals in water would change color. One interesting use for his invention was for house wives to test whether their husbands had been drinking before letting them in the house.
The first practical roadside breath-testing device intended for use by the police was the
drunkometer. The drunkometer was developed by Professor Rolla H. Harger in 1938 The drunkometer collected a motorist's breath sample directly into a balloon inside the machine. The breath sample was then pumped through an acidified
potassium permanganatePotassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...
solution. If there was alcohol in the breath sample, the solution changed colour. The greater the colour change, the more alcohol there was present in the breath.
In late 1927, in a case in Marlborough, England, a Dr. Gorsky, Police Surgeon, asked a suspect to inflate a football bladder with his breath. Since the 2 liters of the man's breath contained 1.5 ml of ethanol , Dr. Gorsky testified before the court that the defendant was "50% drunk".
Though technologies for detecting alcohol vary, it is widely accepted that Dr. Robert Borkenstein (1912–2002), a captain with the Indiana State Police and later a professor at Indiana University at Bloomington, is regarded as the first to create a device that measures a subject's blood alcohol level based on a breath sample. In 1954, Borkenstein invented his breathalyzer, which used chemical oxidation and photometry to determine alcohol concentration. Subsequent breathalyzers have converted primarily to
infrared spectroscopyInfrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
. The invention of the breathalyzer provided law enforcement with a non-invasive test providing immediate results to determine an individual's breath alcohol concentration at the time of testing. Also, the breath alcohol concentration test result itself can vary between individuals consuming identical amounts of alcohol due to gender, weight, and genetic pre-disposition.
Chemistry
When the user exhales into a breathalyzer, any
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
present in their breath is oxidized to
acetic acidAcetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
at the
anodeAn anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
:
CH
3CH
2OH(g) + H
2O(l) → CH
3CO
2H(l) + 4H
+(aq) + 4e
-
At the
cathodeA cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
, atmospheric oxygen is
reducedRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
:
O
2(g) + 4H
+(aq) + 4e
- → 2H
2O(l)
The overall reaction is the oxidation of ethanol to acetic acid and water.
CH
3CH
2OH(l) + O
2(g) → CH
3COOH(l) + H
2O(l)
The electrical current produced by this reaction is measured by a microprocessor,and displayed as an approximation of overall
blood alcohol contentBlood alcohol content , also called blood alcohol concentration, blood ethanol concentration, or blood alcohol level is most commonly used as a metric of alcohol intoxication for legal or medical purposes....
(BAC) by the Alcosensor.
Law enforcement
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
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
in one's breath. Two breathalyzer technologies are most prevalent. Desktop analyzers generally use infrared spectrophotometer technology, electrochemical
fuel cellA fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
technology, or a combination of the two. 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.
Consumer use
There are many models of consumer or personal breath alcohol testers on the market. These hand-held devices are generally less expensive than the devices used by law enforcement. Most retail consumer breath testers use semiconductor-based sensing technology, which is less expensive, less accurate, and less reliable than fuel cell and infrared devices.
All breath alcohol testers sold to consumers in the United States are required to be certified by the
Food and Drug AdministrationThe Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
, while those used by law enforcement must be approved by the Department of Transportation's
National Highway Traffic Safety AdministrationThe National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...
.
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. 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. 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. No semiconductor device has ever been approved for evidential use (to stand-up in a court of law) by any State Law Enforcement Agencies or the U.S. Department of Transportation.
Breath test evidence in the United States
The breath alcohol content reading is used in criminal prosecutions in two ways. The operator of a vehicle whose reading indicates a BrAC over the legal limit for driving will be charged with having committed an
illegal per seThe term illegal per se means that the act is inherently illegal. Thus, an act is illegal without extrinsic proof of any surrounding circumstances such as lack of scienter or other defenses...
offense: that is, it is automatically illegal throughout the United States to drive a vehicle with a BrAC of 0.08 or higher. One exception is the State of Wisconsin, where a first time drunk driving offense is normally a civil ordinance violation.
The uniformity is due to Federal guidelines, since motor vehicle laws are States'; in earlier years the range of the threshold varied considerably between States. The breathalyzer reading will be offered as evidence of that crime, although the issue is what the BrAC was at the time of driving rather than at the time of the test. Some jurisdictions now allow the use of breathalyzer test results without regard as to how much time passed between operation of the vehicle and the time the test was administered. The suspect will also be charged with
driving under the influence of alcoholDrunk driving is the act of operating and/or driving a motor vehicle while under the influence of alcohol and/or drugs to the degree that mental and motor skills are impaired...
(sometimes referred to as driving or operating while intoxicated). While BrAC tests are not necessary to prove a defendant was under the influence, laws in most states require the jury to presume that he was under the influence if his BrAC is found and believed to be over 0.08 (grams of alcohol/210 liters breath) when driving. This is a
rebuttable presumptionBoth in common law and in civil law, a rebuttable presumption is an assumption made by a court, one that is taken to be true unless someone comes forward to contest it and prove otherwise. For example, a defendant in a criminal case is presumed innocent until proved guilty...
, however: the jury can disregard the test if they find it unreliable or if other evidence establishes a reasonable doubt.
Infrared instruments are also known as "evidentiary breath testers" and generally produce court-admissible results. Other instruments, usually hand held in design, are known as "preliminary breath testers" (PBT), and their results, while valuable to an officer attempting to establish probable cause for a drunk driving arrest, are generally not admissible in court. Some states, such as Idaho, permit data or "readings" from hand-held PBTs to be presented as evidence in court. If at all, they are generally only admissible to show the presence of alcohol or as a pass-fail field sobriety test to help determine probable cause to arrest.
South DakotaSouth Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
does not permit data from any type of breath tester, and relies entirely on blood tests to ensure accuracy.
Common sources of error
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. The temperature of the subject is also very important.
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.
HyperventilationHyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...
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%.
Some breath analysis machines assume a
hematocritThe hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
(cell volume of blood) of 47%. However, hematocrit values range from 42 to 52% in men and from 37 to 47% in women. A person with a lower hematocrit will have a falsely high BAC reading.
Research indicates that breath tests can vary at least 15% from actual blood alcohol concentration. An estimated 23% of individuals tested will have a BAC reading higher than their true BAC. Police in Victoria, Australia, use breathalyzers that give a recognized 20% tolerance on readings. Noel Ashby, former Victoria Police Assistant Commissioner (Traffic & Transport), claims that this tolerance is to allow for different body types.
Calibration
Many handheld breathalyzers sold to consumers use a silicon oxide sensor (also called a semiconductor sensor) to determine the blood alcohol concentration. These sensors 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.
Calibration is the process of checking and adjusting the internal settings of a breathalyzer by comparing and adjusting its test results to a known alcohol standard. Law enforcement breathalyzers are meticulously maintained and re-calibrated frequently to ensure accuracy.
There are two methods of calibrating a precision fuel cell breathalyzer, the Wet Bath and the Dry Gas method. 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.
The Dry-Gas Method utilizes a portable calibration standard which is a precise mixture of alcohol and inert nitrogen available in a pressurized canister. Initial equipment costs are less than alternative methods and the steps required are fewer. The equipment is also portable allowing calibrations to be done when and where required.
The Wet Bath Method utilizes an alcohol/water standard in a precise specialized alcohol concentration, contained and delivered in specialized simulator equipment. Wet bath apparatus has a higher initial cost and is not intended to be portable. The standard must be fresh and replaced regularly.
Some semiconductor models are designed specifically to allow the sensor module to be replaced without the need to send the unit to a calibration lab.
Non-specific analysis
One major problem with older breathalyzers is non-specificity: the machines not only identify the ethyl alcohol (or
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
) found in alcoholic beverages, but also other substances similar in molecular structure or reactivity.
The oldest breathalyzer models pass breath through a solution of
potassium dichromate, which oxidizes ethanol into
acetic acidAcetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, changing color in the process. A monochromatic light beam is passed through this sample, and a detector records the change in intensity and, hence, the change in color, which is used to calculate the percent alcohol in the breath. However, since potassium dichromate is a strong oxidizer, numerous alcohol groups can be oxidized by it, producing false positives. This source of false positives is unlikely as very few other substances found in exhaled air are oxidizable.
Infrared-based breathalyzers project an infrared beam of radiation through the captured breath in the sample chamber and detect the
absorbance of the compound as a function of the
wavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of the beam, producing an absorbance spectrum that can be used to identify the compound, as the absorbance is due to the harmonic vibration and stretching of specific bonds in the molecule at specific wavelengths (see
infrared spectroscopyInfrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
). The characteristic bond of alcohols in infrared is the O-H bond, which gives a strong absorbance at a short wavelength. The more light is absorbed by compounds containing the
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
group, the less reaches the detector on the other side—and the higher the reading. Other groups, most notably aromatic rings and carboxylic acids can give similar absorbance readings.
Interfering compounds
Some natural and volatile interfering compounds do exist, however. For example, the
National Highway Traffic Safety AdministrationThe National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...
(NHTSA) has found that dieters and diabetics may have
acetoneAcetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
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.
Substances in the environment can also lead to false BAC readings. For example, methyl tert-butyl ether (MTBE), a common gasoline additive, has been alleged anecdotally to cause false positives in persons exposed to it. Tests have shown this to be true for older machines; however, newer machines detect this interference and compensate for it. Any number of other products found in the environment or workplace can also cause erroneous BAC results. These include compounds found in
lacquerIn a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
, paint remover,
celluloidCelluloid is the name of a class of compounds created from nitrocellulose and camphor, plus dyes and other agents. Generally regarded to be the first thermoplastic, it was first created as Parkesine in 1862 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is...
,
gasolineGasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
, and cleaning fluids, especially ethers, alcohols, and other
volatileIn chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...
compounds.
Homeostatic variables
Breathalyzers assume that the subject being tested has a 2100-to-1 partition ratio in converting alcohol measured in the breath to estimates of alcohol in the blood. If the instrument estimates the BAC, then it measures weight of alcohol to volume of breath, so it will effectively measure grams of alcohol per 2100 ml of breath given. This measure is in direct proportion to the amount of grams of alcohol to every 1 ml of blood. Therefore, there is a 2100-to-1 ratio of alcohol in blood to alcohol in breath. 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 (and US legal) 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 2100-to-1 partition ratio in accordance with William
Henry's lawIn physics, Henry's law is one of the gas laws formulated by William Henry in 1803. It states that:An equivalent way of stating the law is that the solubility of a gas in a liquid at a particular temperature is proportional to the pressure of that gas above the liquid...
, 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. This ratio is constant at a given temperature. The human body is 37 degrees Celsius on average. Breath leaves the mouth at a temperature of 34 degrees Celsius. Alcohol in the body obeys Henry's Law as it is a volatile compound and diffuses in body water. 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, the instrument is calibrated at a ratio of 2100:1, 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. Studies suggest that about 1.8% of the population have a partition ratio below 2100:1. Thus, a machine using a 2100-to-1 ratio could actually overestimate the BAC. As much as 14% of the population has a partition ratio above 2100, thus causing the machine to under-report the BAC. Further, the assumption that the test subject's partition ratio will be average—that there will be 2100 parts in the blood for every part in the breath—means that accurate analysis of a given individual's blood alcohol by measuring breath alcohol is difficult, as the ratio varies considerably. Other studies suggest that women on average have a lower partition ratio than men, leading some to suggest that breathalyzers might be inherently biased against women.
Variance in how much one breathes out can also give false readings, usually low. This is due to biological variance in breath alcohol concentration as a function of the volume of air in the lungs, an example of a factor which interferes with the liquid-gas equilibrium assumed by the devices. The presence of volatile components is another example of this; mixtures of volatile compounds can be more volatile than their components, which can create artificially high levels of ethanol (or other) vapors relative to the normal biological blood/breath alcohol equilibrium.
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. 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.
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 Belching involves the release of gas from the digestive tract through the mouth. It is usually accompanied with a typical sound and, at times, an odor...
. This causes the liquids and/or gases from the stomach—including any alcohol—to rise up into the soft tissue of the
esophagusThe esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
and oral cavity, where it will stay until it has dissipated. The American Medical Association concludes in its
Manual for Chemical Tests for Intoxication (1959): "True reactions with alcohol in expired breath from sources other than the alveolar air (eructation, regurgitation, vomiting) will, of course, vitiate the breath alcohol results." 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. Instruments such as the Intoxilyzer 5000 also feature a "slope" parameter. This parameter detects any decrease in alcohol concentration of 0.006 g per 210 L of breath in 0.6 second, a condition indicative of residual mouth alcohol, and will result in an "invalid sample" warning to the operator, notifying the operator of the presence of the residual mouth alcohol. PBT's, however, feature no such safeguard.
Acid reflux, or
gastroesophageal reflux diseaseGastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...
, can greatly exacerbate the mouth-alcohol problem. The stomach is normally separated from the throat by a valve, but when this valve becomes herniated, there is nothing to stop the liquid contents in the stomach from rising and permeating the esophagus and mouth. The contents—including any alcohol—are then later exhaled into the breathalyzer.
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.
Testing during absorptive phase
Absorption of alcohol continues for anywhere from 20 minutes (on an empty stomach) to two-and-one-half hours (on a full stomach) after the last consumption. Peak absorption generally occurs within an hour. During the initial absorptive phase, the distribution of alcohol throughout the body is not uniform. Uniformity of distribution, called equilibrium, occurs just as absorption completes. In other words, some parts of the body will have a higher blood alcohol content (BAC) than others. One aspect of the non-uniformity before absorption is complete is that the BAC in arterial blood will be higher than in venous blood. Laws generally require blood samples to be venous.
During the initial absorption phase, arterial blood alcohol concentrations are higher than venous. After absorption, venous blood is higher. This is especially true with
bolusIn medicine, a bolus is the administration of a medication, drug or other compound that is given to raise its concentration in blood to an effective level...
dosing. With additional doses of alcohol, the body can reach a sustained equilibrium when absorption and elimination are proportional, calculating a general absorption rate of 0.02/drink and a general elimination rate of 0.015/hour. (One drink is equal to 1.5 ounces of liquor, 12 ounces of beer, or 5 ounces of wine.)
Breath alcohol is a representation of the equilibrium of alcohol concentration as the blood gases (alcohol) pass from the (arterial) blood into the lungs to be expired in the breath. The venous blood picks up oxygen for distribution throughout the body. Breath alcohol concentrations are generally lower than blood alcohol concentrations, because a true representation of blood alcohol concentration is only possible if the lungs were able to completely deflate. Vitreous (eye) fluid provides the most accurate account of blood alcohol concentrations.
Retrograde extrapolation
The breathalyzer test is usually administered at a police station, commonly an hour or more after the arrest. Although this gives the BrAC at the time of the test, it does not by itself answer the question of what it was at the time of driving. The prosecution typically provides an estimated alcohol concentration at the time of driving utilizing retrograde extrapolation, presented by expert opinion. This involves projecting back in time to estimate the BrAC level at the time of driving, by applying the physiological properties of absorption and elimination rates in the human body.
Extrapolation is calculated using five factors and a general elimination rate of 0.015/hour.
For example: Time of breath test-10:00pm...Result of breath test-0.080...Time of driving-9:00pm (stopped by officer)...Time of last drink-8:00pm...Last food-12:00pm
Using these facts, an expert can say the person's last drink was consumed on an empty stomach, which means absorption of the last drink (at 8:00) was complete within one hour-9:00. At the time of the stop, the driver is fully absorbed. The test result of 0.080 was at 10:00. So the one hour of elimination that has occurred since the stop is added in, making 0.080+0.015=0.095 the approximate breath alcohol concentration at the time of the stop.
Photovoltaic assay
The photovoltaic assay, used only in the dated Photo Electric Intoximeter (PEI), is a form of breath testing rarely encountered today. The process works by using photocells to analyze the color change of a
redoxRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
(oxidation-reduction) reaction. A breath sample is bubbled through an aqueous
solutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
of
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
,
potassium dichromate, and
silver nitrateSilver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
. The
silver nitrateSilver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
acts as a catalyst, allowing the
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
to be oxidized at an appreciable rate. The requisite acidic condition needed for the reaction might also be provided by the
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. In
solutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
,
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
reacts with the
potassium dichromate, reducing the dichromate
ionAn ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
to the
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
(III)
ionAn ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
. This reduction results in a change of the
solutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
's color from red-orange to green. The reacted
solutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
is compared to a
vialA vial is a relatively small glass vessel or bottle, especially used to store medication as liquids, powders or in other forms like capsules. They can also be sample vessels; e.g., for use in autosampler devices in analytical chromatography.The glass can be colourless or coloured, clear or amber...
of non-reacted
solutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
by a photocell, which creates an
electric currentElectric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
proportional to the degree of the color change; this current moves the needle that indicates BAC.
Like other methods, breath testing devices using chemical analysis are somewhat prone to false readings.
CompoundsA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
that have compositions similar to
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
, for example, could also act as reducing agents, creating the necessary color change to indicate increased BAC.
Breathalyzer myths
There are a number of substances or techniques that can supposedly "fool" a breathalyzer (i.e., generate a lower
blood alcohol contentBlood alcohol content , also called blood alcohol concentration, blood ethanol concentration, or blood alcohol level is most commonly used as a metric of alcohol intoxication for legal or medical purposes....
).
A 2003 episode of the popular science television show
MythBustersMythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...
tested a number of methods that supposedly allow a person to fool a breathalyzer test. The methods tested included
breath mintsA mint is a candy characterized by the presence of mint flavoring or real mint oil, whether it be peppermint oil, spearmint oil, or another natural or artificial source...
,
onionThe onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
s,
dentureDentures are prosthetic devices constructed to replace missing teeth, and which are supported by surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable, however there are many different denture designs, some which rely on bonding or clasping onto teeth or dental...
cream,
mouthwashMouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...
, pennies and batteries; all of these methods proved ineffective. The show noted that using items such as
breath mintsA mint is a candy characterized by the presence of mint flavoring or real mint oil, whether it be peppermint oil, spearmint oil, or another natural or artificial source...
,
onionThe onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
s,
dentureDentures are prosthetic devices constructed to replace missing teeth, and which are supported by surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable, however there are many different denture designs, some which rely on bonding or clasping onto teeth or dental...
cream and
mouthwashMouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...
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, if any, it appeared that using mouthwash only raised the BAC. 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 — 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 vapor), an oxidizing gas (such as N
2O, Cl
2, O
3, etc.) that would fool a fuel cell type detector, or an organic interferent to fool an infrared absorption detector. The infrared absorption detector is more vulnerable to interference than a laboratory instrument measuring a continuous absorption spectrum since it only makes measurements at particular discrete wavelengths. However, due to the fact that any interference can only cause higher absorption, not lower, the estimated
blood alcohol contentBlood alcohol content , also called blood alcohol concentration, blood ethanol concentration, or blood alcohol level is most commonly used as a metric of alcohol intoxication for legal or medical purposes....
will be overestimated.
Additionally, Cl
2 is rather toxic and corrosive.
A 2007 episode of the Spike network's show
ManswersMANswers is a late night comedy series that premiered on Spike on September 19, 2007.The series is produced by reality television production company, SuperDelicious, and airs on Spike. The executive producers are Kyle Danielson the Third, Adam Cohen, Cara Tapper, Joanna Vernetti, Akifumi Takuma and...
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-coated coin such as a penny. 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.
Products that interfere with testing
On the other hand, products such as mouthwash or
breath sprayBreath spray is a product sprayed into the mouth for the purpose of eliminating or covering up halitosis. It is occasionally advertised as being for smokers or those who dip tobacco, and occasionally to cover up the smell of cigar smoking...
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. (Also see the discussion of the "slope parameter" of the Intoxilyzer 5000 in the "Mouth Alcohol" section above.)
This was clearly illustrated in a study conducted with Listerine mouthwash on a breath machine and reported in an article entitled "Field Sobriety Testing: Intoxilyzers and Listerine Antiseptic" published in the July 1985 issue of
The Police Chief (p. 70). Seven individuals were tested at a police station, with readings of 0.00%. Each then rinsed his mouth with 20 milliliters of Listerine mouthwash for 30 seconds in accordance with directions on the label. All seven were then tested on the machine at intervals of one, three, five and ten minutes. The results indicated an average reading of 0.43 blood-alcohol concentration, indicating a level that, if accurate, approaches lethal proportions. After three minutes, the average level was still 0.020, despite the absence of any alcohol in the system. Even after five minutes, the average level was 0.011.
In another study, reported in 8(22) Drinking/Driving Law Letter 1, a scientist tested the effects of Binaca breath spray on an Intoxilyzer 5000. He performed 23 tests with subjects who sprayed their throats and obtained readings as high as 0.81—far beyond lethal levels. The scientist also noted that the effects of the spray did not fall below detectable levels until after 18 minutes.
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