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Understanding the mechanics of breath testing devices

On Behalf of | Apr 2, 2021 | drunk driving defense |

If and when you face drunk driving charges in Florida, you may think that the result of a blood test supposedly confirming your intoxication serves as insurmountable proof of your guilt. Yet many of those who come to see us here at Campbell & Madden, PLLC often express surprise upon learning that legal authorities may view such results as unreliable.  

Why is this? Much of it has to do with how breath testing devices generate their readings. Understanding this process may provide you with the information needed to challenge the results of a breath test authorities may attempt to use against you.  

How alcohol ends up on your breath

When you drink alcohol, the exact form of alcohol consumed is ethanol. This is a water-soluble compound, which means it can permeate the membrane surfaces through a process known as “passive diffusion.” This allows the ethanol you consume to pass through the linings of the organs of your gastrointestinal tract and enter into your bloodstream. Once there, the veins then carry it throughout your body, eventually arriving in your lungs.  

Upon entering your lungs, some of the ethanol vaporizes due to the oxygen contained therein. That vaporized ethanol then leaves your body as you breathe. As this process continues, the ratio between the blood on your breath and that of your blood remains in equilibrium.  

Your blood-to-breath ratio

According to the Alcohol Pharmacology Education Partnership, breath testing devices use a baseline assumption of a blood-to-breath ratio of 2100:1 when generating readings. Yet in reality, your blood-to-breath ratio can range anywhere from 1500:1 to 3000:1 (depending on various factors). This contributes to some estimating that breath testing devices having a margin of error as high as 50%.  

You can find more information on challenging drunk driving charges throughout our site.