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What is a Preliminary Breath Test?

A preliminary breath test (PBT) is considered a field sobriety test. The purpose of this test is to determine if the officer has probable cause to make a DUI arrest. The officer may ask you to blow into a small hand-held breath testing device. This is a voluntary test in most jurisdictions and you should refuse to take it. However, upon your refusal, the officer can place you under arrest and take you to the police station where you will be required to submit to a formal chemical test of your breath, blood or urine.

Why Are Portable Breath Machines Unreliable?
Most portable breath machines are unreliable because they measure the amount of alcohol in the individual’s breath rather than the actual BAC level. Errors can occur due to:

• Defective equipment
• Improper calibration (most hand-held devices require calibration every six months)
• Test was improperly administered by the officer
• False readings due to medical conditions, such as acid reflux disease or diabetes
• False positive due to using mouthwash containing alcohol

Individuals who regularly work with certain types of chemicals, such as cleaning fluids or paint removers may also have a false positive result.