A certified ignition interlock device is a breath-analyzing instrument that is wired to the vehicle's ignition and installed on the vehicle dashboard, along with a camera and GPS. Before the vehicle can be started, the driver first must exhale into the device. If the interlock detects alcohol on the breath, the engine will not start. The device measures your breath alcohol content (BAC) level. You'll only be able to start your vehicle if your BAC level is under 0.020.