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Reviewing the fundamentals of breath test BAC measurements

On Behalf of | Jun 28, 2022 | DUI/DWI

Were one to poll a random number of people in New York about their immediate thoughts regarding drunk driving charges, responses of various nature might still come up with a common theme detailing a roadside scene of a person blowing into a handheld breath testing device.

This prompts that question the many potential clients bring to the team here at James Kleinbaum Attorney At Law P.C.: why would law enforcement officers rely on a test of one’s breath to measure the alcohol content of their blood? Understanding the relationship between the content of alcohol on one’s breath to one’s blood may prove useful to one looking to challenge the validity of DWI charges pending against them.

How does alcohol get to one’s breath?

The exact type of alcohol one consumes when drinking is ethanol. This is a water-soluble compound, whose composition allows it to permeate membrane surfaces through a process known as “passive diffusion.” This is how ethanol enters the bloodstream from the organs of the gastrointestinal tract. Once in the blood, the veins carry the ethanol throughout the body, eventually arriving in the lungs.

In the lungs, some of the ethanol vaporizes upon coming into contact with oxygen. This gaseous ethanol then escapes the body as one breathes. The concentration between the alcohol on one’s breath between that which remains in their blood remains in equilibrium.

What allows breath testing devices to measure BAC?

It is through this concept of equilibrium that breath testing devices measure one’s blood-alcohol content. These devices measure the alcohol content of one’s breath, then use an assumed blood-to-breath ratio to estimate one’s BAC. According to the Alcohol Pharmacology Education Partnership, this ratio is 2100:1. The problem, however, is that research shows the average person’s alcohol blood-to-breath ratio ranges from 1500:1 to 3000:1, opening up breath test results to serious scrutiny.