A frequent question we receive here at LifeSafer is from curious people wanting to understand how an electronic device like an Ignition Interlock measures your breath alcohol levels. It would seem like a complicated matter but is actually quite simple.
When a person consumes alcohol, that alcohol will show up in the breath because it gets absorbed from various body areas such as the mouth, throat, stomach and even the intestines. These areas then deposit the alcohol into the bloodstream.
Alcohol is not digested after absorption, nor is it chemically changed once it enters the bloodstream. As the blood passes through the lungs, some of the alcohol crosses over membranes of the lung’s air sacs and then out into the air. The concentration of alcohol in the air is therefore directly related to the concentration of the alcohol levels in the blood. As the alcohol from the lungs is exhaled, it can be detected and measured by an Alcohol Interlock Device.
Modern Ignition Interlock Devices like the ones manufactured by LifeSafer use an ethanol type fuel cell as a sensor. A fuel cell sensor is an electrochemical device in which alcohol reacts with a catalytic electrode surface such as platinum to generate an Electric current. This current can then be converted into an alcohol equivalent reading and be measured.
If a person has been drinking alcohol, their measurement of breath alcohol levels may or may not be higher than those allowed by individual state laws. If a person has an Ignition Interlock Device installed in their car, their breath alcohol readings will determine if they can start and properly run their motor vehicle or not.