Breathalyzer

From ArticleWorld

Now you can measure anyone's exact alcohol level with a portable breath tester. Simply blow into the tester and your blood alcohol level will be displayed in seconds. A breathalyzer is a device for estimating blood alcohol content (BAC) from a breath sample. "Breathalyzer" is the brand name of a model made by one manufacturer of these instruments (originally Smith and Wesson, later National Draeger), but has become a genericized trademark for all such instruments. Intoxilyzer, Intoximeter, Alcotest, Alcosensor and Datamaster are the other most common brand names in use today.

A breath analyzer, or breathalyzer, is a battery-operated device that can reveal a person's blood alcohol content (BAC) by sampling the breath. Law enforcement has used breathalyzers for many years, but a breath analyzer can also be handy for individuals. Party guests can avail themselves of a breathalyzer to ensure they can legally and safely get behind the wheel to drive home.

A breath analyzer can detect BAC because alcohol does not change chemical composition within the body. Instead, it is absorbed by the stomach and intestines to enter the bloodstream. Inside the bloodstream it travels throughout the body, including lung sacs called alveoli, where alcohol molecules are mixed with exhaled air. The ratio for alcohol found in the breath to alcohol in the blood is 2,100:1. Hence, by measuring the concentration of alcohol in the breath, the breath analyzer can easily calculate blood alcohol content.

Breath analyzers don't 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 one's breath. Three technologies are in use: evidentiary machines, used by police forces, which generally utilize infrared spectrophotometer technology; less accurate hand-held electrochemical fuel cell-based instruments, used by officers in the field and commonly called PBT (preliminary breath test) or PAS (preliminary alcohol screening); and semiconductor oxide based testers, cheapest and least reliable but becoming increasingly popular for personal and professional testing applications.

The breath alcohol reading is used in criminal prosecutions in two ways. Unless the suspect refuses to submit to chemical testing, he will be charged with a violation of the so-called illegal per se law: it is a misdemeanor in all states to drive a vehicle with a BAC of .08% or higher (the forbidden level is lower for drivers under 21). The breathalyzer reading will be offered as evidence of that crime, although the issue is what the BAC was at the time of driving rather than at the time of the test. The suspect will also be charged with driving under the influence of alcohol (sometimes referred to as driving or operating while intoxicated). While BAC 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 BAC was over .08% when driving. This is a rebuttable presumption, however: the jury can disregard the test if they find it unreliable or if other evidence establishes a reasonable doubt.

Though technologies for detecting alcohol vary, it's widely accepted that Dr. Robert Borkenstein (1912-2002), a captain with the Indiana State Police and later a professor at the University of Indiana, is regarded as the first to create a device that measures a subject's alcohol level based on a breath sample. In 1954, Borkenstein invented his breathalyzer, that used chemical oxidation and photometry to determine alcohol concentration. The invention of the breathalyzer provided law enforcement with a non-invasive test with immediate result reporting that can be used to determine an individual's level of intoxication. The various versions of the Breathalyzer were made by Smith and Wesson, the gun manufacturer, until the sale of the line to the German company National Draeger.

A major problem with some machines is that they not only identify the ethyl alcohol (or ethanol) found in alcohol beverages, but also other substances similar in molecular structure. Those machines identify any compound containing the methyl group structure. Over one hundred compounds can be found in the human breath at any one time and 70 to 80 percent of them contain methyl group structure and will be incorrectly detected as ethyl alcohol. Importantly, the more different ethyl group substances the machine detects, the higher the false BAC estimate will be.

The National Highway Traffic Safety Administration (NHTSA) has found that dieters and diabetics can have acetone levels hundreds and 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. Substances in the environment can also lead to false BAC readings. For example, an alcohol-free subject was asked to apply a pint of contact cement to a piece of plywood and then to apply a gallon of oil-base paint to a wall. The total activity lasted about an hour. Twenty minutes later the subject was tested on an Intoxilyzer, which registered a BAC of .12 percent. This level is 50% higher than a BAC of .08, which constitutes legal intoxication.

Any number of other products found in the environment can cause erroneous BAC results. These include compounds found in lacquers, paint removers, celluloid, gasoline, and cleaning fluids. Other common things that can cause false BAC levels are alcohol, blood or vomit in the subject's mouth, electrical interference from cell phones and police radios, tobacco smoke, dirt, and moisture. Breath testers can be very sensitive to temperature and will give false readings if not adjusted or recalibrated to account for ambient or surrounding air temperatures.

The "Breathalyzer" brand breath-testing device operates by using photocells to analyze the colour change of an oxidation-reduction reaction. A breath sample is bubbled through an aqueous solution of sulfuric acid, potassium dichromate, and silver nitrate. The silver nitrate acts as a catalyst, allowing the alcohol to be oxidized at an appreciable rate. The requisite acidic condition needed for the reaction might also be provided by the sulfuric acid. In solution, ethanol reacts with the potassium dichromate, reducing the dichromate ion to the chromium (III) ion. This reduction results in a change of the solution's colour from red-orange to green. The reacted solution is compared to a vial of nonreacted solution by a photocell, which creates an electric current proportional to the degree of the colour change; this current moves the needle that indicates BAC.

A common myth is that breath testers can be "fooled" (that is, made to generate estimates making one's blood alcohol content appear lower) by using certain substances. An episode of the Discovery Channel's MythBusters tested substances usually recommended in this practice -- including breath mints, mouthwash, and onion -- and found them to be ineffective. Adding an odor to mask the smell of alcohol might fool a person, but does not change the actual alcohol concentration in the body or on the breath.

On the other hand, products such as mouthwash or breath spray can "fool" breath machines by significantly raising test results. Listerine, for example, contains 27% alcohol; because the breath machine will assume the alcohol is coming from alcohol in the blood diffusing into the lung rather than directly from the mouth, it will apply a "partition ratio" of 2100:1 in computing blood alcohol concentration -- resulting in a false high test reading.

Like other methods, the "Breathalyzer" chemical analysis is somewhat prone to false readings; compounds which have compositions similar to ethanol could also act as reducing agents, creating the necessary colour change to indicate increased BAC. 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.