Former District Attorney Protecting
The Accused And Seeking Justice For The Injured.

Breath and BAC

On Behalf of | Mar 29, 2018 | DWI |

There is typically one number that people in Mineola associate with drunk driving: .08. That is the blood-alcohol content measurement that is almost universally accepted as defining intoxication. Yet it is not the only number related to BAC that New York drivers need to worry about. Per the New York Department of Motor Vehicles, a BAC or .05 percent is enough to label a driver as being impaired, while a BAC of .18 percent qualifies one to be charged with aggravated DWI. 

With all of the talk about blood-alcohol levels, however, a pressing question arises: how is it that a breathalyzer device (which measure one’s breath) is used to determine BAC? The Alcohol Pharmacology Education Partnership offers an explanation of what a person’s breath may say about the alcohol content of their blood. 

Ethanol is the exact type of alcohol used in drinks such as: 

  • Beer 
  • Wine
  • Liquor

It is water-soluble, meaning that it can pass through membranes in the body via a process known as passive diffusion. Thus, after being consumed, ethanol moves through the lining of the stomach and small intestines into the bloodstream. It is then carried to the heart, then to the lungs where some of it vaporizes into a gas that accumulates in the alveoli (the lung sac). The gaseous ethanol then is carried out with each breath. 

This process continues, with the remaining ethanol in the blood vaporizing in the lungs at a rate that maintains equilibrium. What this means is that as one breaths, his or her BAC lowers. This dynamic process may contribute to the unreliability of breathalyzer measurements. While they are able to measure BAC, the fact that a person’s BAC is constantly changing with each breath may contribute to a much wider margin of error.