The ignition interlock system was designed to check a person's breath for alcohol before allowing a motor vehicle to start. Every time he or she wants to use the car—regardless of the time of day—the person has to blow into the device. Only when he or she is cleared will the vehicle start.
So, do you have to use this system if you get a DUI in Pennsylvania? As you'll see, the answer can be both yes and no, depending on the circumstances.