The problem with breath machines and so-called breathalyzers
The problem with breath machines is that the design of the machine leaves much to be desired.
First, let’s get our language correct. They don’t call them breathalyzers anymore. The roadside breath test is called a PAS test, and the test at the station is called a “Chemical Breath Test.” Now that this common problem in nomenclature is taken care of, what are the problems with breath alcohol testing machines?
Non-specific analysis–the inability of the machine to differentiate alcohol from other similar compounds–is a problem common to all breath machines. The only difference is how badly they mistake other compounds with ethyl alcohol and how many compounds they cannot differentiate from alcohol. Put simply, design of the machine is everything and the design of many breath machines leaves much to be desired.
The oldest breath machines (commonly referred to as “breathalyzers” and no longer in use) transfer your breath through a solution of potassium dichromate., This oxidizes ethanol into acetic acid, and alters its color in the process. A monochromatic light beam is then passed through this sample, and a detector reads the change in intensity of the light beam (and, hence, the change in color), which is used to calculate the percentage of alcohol in the breath. However, since potassium dichromate is a strong oxidizer, numerous alcohol groups can be oxidized by it, producing false positives.
Infrared Breath Machines and Non-Specific Analysis
Breathalyzers have been replaced by machines that test your BAC using two tests- infrared technology, and an electrochemical fuel cell. Infrared-based breath machines project an infrared beam of radiation through the captured breath that you have blown into the breath machine’s sample chamber. Light projected by the infrared beam gets absorbed by alcohol in the chamber, dimming the light at the other end of the chamber. The dimmer the light (i.e. the more light absorbed by alcohol) the higher your BAC. Put another way, the more light that is absorbed by compounds containing the alcohol group, the less light reaches the detector on the other side—and thus the higher the reading.
The problem is that many types of chemicals have an absorbance factor that is similar to alcohol, and can be confused for alcohol in many infrared machines. Acetone, aromatic rings, ketones and carboxylic acids can give similar absorbance readings to ethyl alcohol.
Some natural and volatile interfering compounds mimic ethyl alcohol. Acetone and ketones are the most common. For example, the National Highway Traffic Safety Administration (NHTSA) has 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, The manufacturers of many fuel cell based systems claim them to be acetone specific and are are also claimed to be non-responsive to substances like acetone. And, in truth, acetone does not appear to pose much of a problem for more modern machines like the Draegar 7110.
False positives can be generated in other ways as well. For example, a study in Spain showed that metered-dose inhalers (MDIs) used by asthmatics can also cause 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. (If you recently used your mouth to siphon gasoline, then you are at risk of a false reading for alcohol in your blood.)
Painters, building contractors, employees at body shops and other workplaces that expose people to fumes from paints, lacquers and fuels can easily generate erroneous BAC results. Causes include compounds found in lacquer, paint remover, celluloid, gasoline, and cleaning fluids, especially ethers, alcohols, and other volatile compounds.
Breath machines operate on the assumption that the subject being tested has a 2100-to-1 partition ratio- which is to say that for every 1 part of ethyl alcohol at the base of your lungs there are 2100 parts in your blood. But this ratio is just an average. .
In fact, most individuals have a partition ratio that is different from the legal “average” of 1 to 2100. And as many as 40% of the people who blow into a roadside breath machine have their actual BAC overstated.
In fact, your actual partition ratio can be as low as 1-900 and as high as 1-3100. And the lower your partition ratio, the greater the breath machine is overstating your BAC. If your partition ratio is 1-1000 then any breath machine will be reporting your BAC as double what it actually is.
Not only do partition ratios vary from person to person, they can also vary in the same person over time.
Partition ratio evidence used to be prohibited in court—it couldn’t even be mentioned before a jury—but with a new California Supreme Court decision it can now be used in any case where you are charged with the “a” count (Vehicle Code 23152(a)) of “driving under the influence of alcohol.”
Mouth Breath Alcohol
A common common cause of false high BAC readings is the existence of mouth breath alcohol. In analyzing a subject’s breath sample, the breath machine assumes that the alcohol that it is measuring comes from alveolar air—that is, air exhaled from deep within your lungs. However, alcohol may have come from the mouth, throat or stomach, for any number of reasons, including GERD, acid reflux, burping, belching or heartburn. To help guard against mouth-alcohol contamination, certified breath-test operators are supposed to, but rarely do, observe a test subject carefully for at least 15–20 minutes before administering the test.
The problem with breath machines analyzing mouth alcohol is that the breath was not absorbed from the stomach and intestines to the blood and 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.
Aside from drinking the most common source of mouth alcohol is from belching or burping. When you belch, the liquids and/or gases from the stomach—including any alcohol—rises up into the soft tissue of the esophagus and oral cavity, where it stays until it is dissipated. This is not a defense to be idly dismissed.
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 continuous observation for at least 15 minutes prior to administering a breath test. What constitutes “continuous observation” leaves much to be desired, however. If you are seated in the back of a squad car and the cop is driving, he cannot be watching you. The courts have still held, however, that this constitutes “continuous observation.”
Breath machines such as the Draegar Intoximeter 7110, the Intoxilyzer 5000 and the Datamaster also feature a so-called “slope detector” that is supposed to find and discount any “spike” in your BAC while you are blowing. This detector is supposed to detect 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. Notice, however, that the slope detector is only looking for a short, brief (0.6 second) spike in your BAC. In many cases, however, mouth breath alcohol can be continuously blown through the machine’s mouthpiece for over 10 seconds. Mouthwash, dentures, gum disease, particles stuck in your teeth containing alcohol–all of these can cause mouth breath alcohol to enter the breath machine for the entire blow.
PAS machines do not have slope detectors. Thus, the appearance of mouth breath alcohol will invalidate any PAS test.
Acid reflux, or gastroesophageal reflux disease, can result in exaggerated false highs. The stomach is normally separated from the throat by a valve, but when this valve is herniated or otherwise rendered inoperable, there is nothing to stop the liquid contents in the stomach from rising and permeating the esophagus and mouth. And a slope detector will not “detect” this continuous condition.
Other Problems with Breath Machines
- Dentures– Mouth breath alcohol can also be caused by dentures. Of course, dentures will trap alcohol.
- Periodontal disease can also create pockets in the gums which will contain the alcohol for longer periods.
- Passionate kissing with a person who is intoxicated can cause elevated highs.
- Mouthwash or breath fresheners such as Binaca can also cause false highs. Mouthwash and/or breath freshener are particularly toxic to breath tests not the least because people use these to disguise the smell of alcohol when the cops pull them over and they are loaded with alcohol. The worst is Listerine with an alcohol content of 27% by volume.
Rising Blood Alcohol
Click here to learn about rising blood alcohol.