Is the breath machine an accurate reading of my blood alcohol level?


Mr. Taylor describes how the breath machine measures a person’s blood alcohol level and the many reasons why the measurement is unreliable. The machine is testing a person’s blood alcohol level at the time the person is tested, no earlier and no later. The breath machines are highly unreliable for several different reasons, including the fact that the machine may not be calibrated correctly or it may not be maintained correctly. Also the machine makes the assumption that all people who breathe into the machine are average, which is an obvious misconception. Lastly, there are physiological differences in people that can alter the machine’s reading, meaning that the conditions and problems that people have can result in the machine giving an inaccurate reading. Some of these conditions include when a person has acid reflux, suffers from diabetes or a disease such as periodontal disease. All of these conditions can cause the machine to give a higher reading of blood alcohol than a person really has.

Show Transcript


First of all, understand that the machine is reading, and not terribly accurately in most cases, is reading your blood alcohol at the time you are tested at the police station. It is not testing it when you were driving, perhaps two hours, hour and a half earlier, and the fact is your blood alcohol is constantly either rising or falling, is part of metabolism. So you may be at 1.0 or 0.09 at the station and 0.07 at the time you were driving. That’s called a fancy term retrograde extrapolation, trying to estimate backwards in time what your blood alcohol was. The second issue is that the breath machines themselves are highly unreliable and inaccurate and there are a number of reasons for this. They may be calibrated incorrectly, they may be maintained incorrectly, they are testing, not you, but an average person, because the computer in the machine is assuming all kinds of things about you being average and the fact is you’re not average. It, for example, is going to multiply your alcohol by twenty-one hundred times to get the amount of alcohol in your blood. That’s an average. You may be very different than that, probably you are going to be very different than that, and that will directly affect the machines’ reading from your true level. Now, finally, there are physiological differences, and by that I mean humans have different problems or conditions that can affect the machine and the machine cannot detect them. For example, if you have GERD or acid reflux, you’re admitting a chemical that the machine is going to accept as alcohol from your lungs and it’s not and it will get a very high reading. If you’re a diabetic, you are going to be breathing out ketons acete, a condition of acetone that is read by the machine as alcohol, even though it is not. And there are a number of different physiological conditions that can cause the problem. If you have periodontal disease, for example, you can trap food and alcohol in your mouth and, again, breathe directly in, and the machine multiplies it twenty-one hundred times because it doesn’t know it didn’t come from the lungs.

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