To Blow or not to blow part 2

This blog entry will briefly discuss how the magic breath machines work and how they spit out that little piece of paper which effects the rest of your life. The following blogs in this multi part series will discuss the particular shortcomings of the EC/IR machine.

A breathalyzer machine is a general term for a machine which tests the amount of alcohol in your breath; they were first developed in the 1940’s for use by the police. In 1954 Dr. Robert Borkenstein of the Indiana State Police invented a machine known as the breathalyzer.

Maryland is presently utilizing a machine known as the EC/IR machine for its DUI and alcohol detection. There are other machines such as Alcotest and DataMaster. These large machines that sit in the police station should not be confused with the PBT or Preliminary Breath Test handheld devices that the officers carry on the street. The PBT device can not be used as evidence against you in court but rather is used to guide the police is making an arrest.

Getting back to the intox machine, in Maryland we use the EC/IR. The EC is the fuel cell or electrochemical sensor and the IR stands for infrared spectroscopy. The machine utilizes both methods in an alleged attempt to be accurate Admittedly, the fuel cell sensor is specific to alcohol, while the IR sensor can be effected by many common breath constituents. The IR uses infrared spectroscopy to identify certain molecules by the way the molecules absorb infrared light, it measures the molecules in near real time in order to determine the best breath sample to evaluate. Molecules constantly vibrate and the vibration changes when the molecule absorbs light. The changes in vibration are the result of bending and stretching of the molecular bonds. Importantly, each time a molecule absorbs IR at different wavelengths, this is what the intox machines are able to measure.

That is, in order to identify the presence and amount of alcohol in the system, the intox machine endeavors to identify the ethanol molecule in a sample of breath. The machine calculates the absorption of the IR light as it passes through the sample breath provided (the the breath chamber of the machine) and based on the amount of light absorbed by the sample, the machine can determine the presence of ethanol alcohol and the amount. The absorbed wavelengths identify the substance, and the amount of IR absorption tells how much alcohol is present.

To put it another way, the machine has a light which it projects through an air sample chamber. Based on a clear breath sample chamber, the machine expects a given amount of light to register at the other end as it passes through special filters designed to look for the ethanol molecule. As the light passes through the filter it is received by a photocell whereupon a calculation determines the amount of light originally dispatched versus light received at the photocell after passing through the specific ethanol (alcohol) filter and magically determines your breath alcohol content.

Yes, but how does the alcohol get into my breath anyway after I consume it?

The alcohol that you drink appears in your breath as it gets absorbed into your blood stream through the mouth, throat, stomach and intestines. The vast majority, roughly 80%, is absorbed in the small intestine after passing through the stomach. It is not digested upon absorption, nor is it changed in the bloodstream. As your blood travels through the lungs, the alcohol in your blood stream exchanges with the air of your alveoli (membranes of the lung) and is then exhaled out of your mouth when you breathe. Therefore, there is an exchange of some alcohol content between your blood and your lungs in the normal body function when you breathe. This allows the officer to test for alcohol on the street or at the station house without having to draw blood.

The proportion of alcohol in your bloodstream to that of exhaled air is calculated in terms of a ratio. The magical intox machines base that ration on 2100:1. That is, for every 1ml (milliliters) of blood, there is 2,100 ml of alveolar air which will allegedly contain the same amount of alcohol. The problem, as we will see in future posts, is that that ratio is not always the same in all people.

Before I leave the topic of how the machine works, let me touch on the fuel cell part of the machine. The fuel cell has two platinum electrodes with a porous acid-electrolyte material. As the breath sample passes from one side of the fuel cell to the other, the platinum oxidizes the alcohol in the sample and produces acetic acide, protons and electrons. The electrons then flow through a wire which is connected to a meter registering current. The more current produced, the more alcohol present in the sample.

Bruce Robinson Maryland DUI Lawyer Serving Baltimore and surrounding counties