There are two types of breathalyzers used in Virginia: 1) the preliminary breath tester (PBT) and 2) the evidential test device (ETD). The biggest difference between these machines is that the PBT is voluntary—you have the right to refuse blowing into a PBT. On the other hand, ETDs are mandatory if you have been arrested for DUI. You may be charged with refusal to submit to a breath test if you refuse to blow into an EDT after being arrested for DUI.
PBTs are handheld devices that police officers use at the scene of the arrest to determine BAC. They are usually kept in the trunk of a police cruiser. They are small, portable machines with a plastic tube or mouthpiece that the driver blows into. PBTs can only be used to justify an arrest; they cannot be used as evidence at trial.
ETDs are different from PBT in several ways. They are not portable. The machine is about the size of large shoebox with a tube to blow into that sticks out from the side. They are usually attached to a printer and keyboard. All ETDs in Virginia are the same make and model (the INTOX EC/IR II’s), and they are found at the police station rather than kept in the police cars. Before blowing into an EDT in Virginia, a driver must be observed for 20 minutes. The driver must also be read a form letter stating that he must submit to the test, that he has the right to observe the results, and that he has a right to receive a copy of the printed results. The results of EDT can be used as evidence at trial.
Remember, the most important difference between PBTs and ETDs is that a driver suspected of DUI does not have to blow into a PBT, but a driver arrested for DUI must submit to being breath-tested by an ETD.