I get asked many questions about the preliminary breath test, or PBT, so I want to try and answer some of the more common ones here.  

1. What is a preliminary breath test? A preliminary breath test, or PBT, is just another field sobriety test.  The officer asks the driver to blow into a small, handheld breath testing device. The BAC reading cannot be used as evidence against the driver.  However, the officer is allowed to write in the report and testify that the test was positive for the presence of alcohol.

2. If I am pulled over, do I have to take a PBT? No, there is no requirement in Pennsylvania that you take a PBT.  It is the same as refusing any other field sobriety test.  

3. Will I lose my driver's license if I refuse to take a PBT? No, since you are not obligated to take the PBT, you will not lose your driver's license if you refuse to take it.

4. Are the results of a PBT test reliable? No, in fact, the results of a PBT test are inherently unreliable.  There are two main types of PBT machines that Pittsburgh area police use; one is a fuel cell device, the other is a gas sensor device and both are unreliable.  The fuel cell devices not only detect alcohol, they will also detect a large number of compounds which may trigger a false positive. The results may also be unreliable due to mouth alcohol (alcohol that is in your mouth due to burping, hiccupping, or many other reasons, within 20 minutes of you blowing into the PBT). A gas sensor device may detect alcohol from sources other than the your breath, such as an open alcohol container or a spilled drink.

5. If I don't have to take a PBT, I won't lose my license for refusing to take one, the results are unreliable and are not admissible as anything more than "testing positive for the presence of alcohol," why do the police use them?  The police use a PBT result in the same manner as they use the result of any other field sobriety test, which is to build probable cause to take you to the police station to take the evidentiary breath test or to the hospital to provide a blood sample.

Remember, do not confuse the PBT with the actual breathalyzer machine.  A PBT is a small, handheld device that the officer will ask you to blow into while you are pulled over on the side of the road.  If you are at the police station and the police are asking you to blow into a machine that an officer cannot hold in his or her hand, this is the evidentiary breath machine and if you refuse to blow into this machine you will lose your driver's license for at least one year.