Timberlake Personal Injury

How Do Breathalyzers Work?

How Do Breathalyzers Work?


If you’ve ever been pulled over for suspicion of DUI in Virginia, there’s a good chance that you were asked to submit to a breathalyzer test. These devices may seem as if they magically measure the amount of alcohol content in your body, but there is some science inside those boxes. The result that a breathalyzer produces could influence an officer’s decision on your arrest, or it may validate an arrest that already took place.

How Alcohol is Detected on Your Breath

When a person has been drinking, you can usually smell alcohol on their breath. This is something that’s highly subjective as the smell could be the same whether you have had one drink or many. A breathalyzer doesn’t “sniff” your breath but rather analyzes the presence of alcohol in your system at the molecular level.

Alcohol molecules are so tiny that they will pass through your stomach’s wall into your blood stream. This happens within minutes after you begin drinking that wine, beer, or other cocktail. After it enters your bloodstream, the alcohol will also travel through your lungs, and some of it will evaporate into your outgoing breath.

How Does a Breathalyzer Work?

When you breathe into a breathalyzer, the device can measure the amount of alcohol in your breath, which translates to your blood alcohol content (BAC). In Virginia, the legal limit is 0.08, but the laws will vary for underage drinkers or those who have a commercial driver’s license. This mathematical estimation of your BAC can be provided by several different varieties of breathalyzer technology.

  • Semiconductor Sensor Breathalyzers. If you have a personal breathalyzer, it is probably one of this variety. These relatively affordable devices will oxidize alcohol molecules using a low-voltage semiconductor that is created from metal oxide. When you breathe into the device, the breathalyzer will oxidize the molecules, and the affected electrical current will produce your BAC. Unfortunately, these machines are also prone to providing false positive results.
  • Fuel-Cell Breathalyzers. A police officer giving a breath test on the side of the road will most likely use one of these devices, which works in a similar fashion to a semiconductor breathalyzer. The difference is that these machines are specifically calibrated for alcohol, so they are more precise.
  • Infrared Spectroscopy Breathalyzers. This is a bulkier and more expensive unit that you will most likely find sitting in a police station. When you breathe into one of these breathalyzer machines, it measures your BAC by sending your breath through infrared light. Alcohol molecules absorb light differently, so they can be identified and then measured.

Are Breathalyzers Accurate?

Some breathalyzers are more accurate than others, but none of them are infallible. This is just one of the reasons why you should speak with a qualified Virginia DUI attorney if you are ever charged with a DUI.

There is a margin of error with most breathalyzers, and there are certain factors that can cast doubt on a positive result. These sensitive machines are supposed to be calibrated at least annually, so failure to do this could result in a test being disqualified. Some breathalyzers may give false results due to such things as acid reflux, blood in the mouth, and body temperature. Natural chemicals such as “ketones” have also been mistaken for alcohol in the bloodstream and returned positive results.            

Should You Agree to Take a Breathalyzer Test in Virginia?

One of the biggest misconceptions about breathalyzer tests is that you are compelled to take one if an officer puts it in front of you during a DUI stop. In Virginia, this is not the case. You do not have to agree to a preliminary breath test (PBT), which is part of the field sobriety test, and the results of one of these tests are not admissible in court.

Virginia is, however, an implied consent state, meaning that you have already given permission for a breath test if you are arrested for DUI. If the authorities charge you and take you to the police station, you must agree to take the test, or you will be subject to additional charges.

Getting arrested for DUI can be a terrifying experience. The truth is that everyone makes mistakes and there is a chance that the police made an error in handling your arrest. The consequences of a DUI conviction can be grave, so this is not something you should leave to chance.

The Pack Law Group can provide the strong defense you need and will take immediate steps to protect your rights. Contact our Bedford office now at (540) 586-7225.