What Makes Preliminary Breath Tests Different from Breathalyzer Tests?
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- June 3, 2025
When police officials stop someone they suspect of drinking and driving, they use breath tests to check if the person is under the influence of alcohol. One common test they use on the road is a preliminary breath test. This test helps officers quickly decide if the driver is intoxicated or not.
However, there is another test called the Breathalyzer test, which is more accurate and usually done at a police station. Many people confuse these two tests, but they are quite different in how they work, when they are used, and how reliable they are.
In this article, we will see the key differences between a preliminary breath test and a Breathalyzer test.
Preliminary breath test
A preliminary breath test (PBT) is typically the first step when a DUI is suspected.
- Purpose of the PBT: The main reason officers use a preliminary breath test is to check if a driver may be driving under the influence of alcohol. It’s a quick way to see if further legal steps, like arrest or more testing, are needed.
- How the test works: This test is simple and fast. The driver blows into a small device, and the machine gives a reading that estimates the level of alcohol in the breath.
- Legal use of PBT results: Although the PBT gives quick results, it’s not strong enough to be used as final evidence in court due to its limitations. It helps the officer make a decision but doesn’t decide guilt by itself.
- Accuracy and limitations: PBTs are helpful, but they are not 100% reliable. Here are some common limitations:
- Environmental factors such as cold weather can affect readings.
- Mouth alcohol (from recent drinks, mouthwash, or burping) may give a false high result.
- The device may be poorly calibrated, giving inaccurate readings.
- Health conditions or medications can sometimes affect the results.
Breathalyzer test
A Breathalyzer test is a more advanced and precise device used by police officials, usually at the police station, to measure a person’s blood alcohol content (BAC).
- Purpose of the Breathalyzer test: The main purpose of the Breathalyzer test is to determine whether a person is intoxicated or not, accurately and with precise measurement, unlike PBT. This helps to prevent false accusations and ensures that no one is wrongly convicted.
- How the test works: You exhale into a mouthpiece, and the breath sample enters a chamber containing a sensor that detects alcohol. The chamber may utilize fuel cell technology or infrared spectroscopy for precise measurement.
- Legal use of Breathalyzer results: Breathalyzer test results carry legal weight and are often used as key evidence in DUI cases. Because they are more precise and standardized, these results can be presented in court to prove or disprove intoxication.
- Accuracy and limitations: It has very few limitations when compared to PBT.
Key differences between them
The key difference between a PBT and a Breathalyzer lies in their testing methods. PBT devices usually use semiconductor sensors, which are quicker but less accurate. In contrast, Breathalyzers rely on advanced technology like fuel cell sensors or infrared spectroscopy, providing more reliable and precise readings of blood alcohol content (BAC). This makes the Breathalyzer more suitable for legal and courtroom use.
Essentially, both the preliminary breath test and the Breathalyzer serve the purpose of detecting alcohol in a person’s breath; however, they differ in terms of accuracy, technology, and legal use.
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