Breath Analysis For Drinking and Driving
Types of Tests:
- Blood Test
- Breath Analysis
- Human Error/Mechanical Malfunction
- Prelimary Alcohol Screening Test
- Urine Test
The percentage of ethanol from alcohol in a person’s blood is the same as the percentage of alcohol in that person’s exhaled breath. Breath tests capture the air as the driver breathes out and determine the alcohol level in the sample of that breath. Breathalyzers are the most commonly used chemical sobriety test due to their accessibility, convenience, and inexpensive cost.
Breath testing is normally performed on the side of the road prior to an arrest or at a police station. The test is performed with a small portable device known as a Preliminary Breath Test (PBT), a breathalyzer, or similar test kits found in most hospitals, clinics and police headquarters.
Breathalyzers, PBT devices, and other similar machines require the subject to blow into the mouthpiece. The device measures the air passing through it and records the level of alcohol in the breath.
The technology behind breath analysis is known as fuel cell science. The system works by technically “burning” the alcohol passing through the device, which generates an electric current. This electric current is measured numerically, providing a Blood Alcohol Content (BAC) count. The current BAC limit for driving in the United States is .08.
Unfortunately, breath tests are not as accurate in determining blood alcohol content as other tests like urine and blood analysis. For example, false BAC readings from breathalyzers may result from minor technology interference, such as a cell phone signal.
Breath tests may also misread the presence of molecularly-similar substances to alcohol in the breath or can be easily altered by a very small existence of vomit or blood in the mouth. At times, even irregular breathing patterns have misrepresented BAC results from breathalyzers.
Technically, the PBT is optional for any driver pulled over upon suspicion of drunk driving. However, two thirds of all states have now passed Administrative License Revocation laws. These laws allow officers to suspend the license of drivers who refuse to take a breath test.
The inaccuracy of the PBT device has led to some states, including Wisconsin, to ban the roadside test altogether. In those states, the breath test must be conducted at the station on a more reliable machine that is less prone to outside elements and human error.