An Ignition Interlock Device, otherwise known as an IID, is a hand-held machine that is installed inside a vehicle. It measures the breath of the driver before they can start the car. The user must blow into the mouthpiece for a certain period, wait for it to calibrate, and then begin operating the vehicle once it passes. Individuals with one or more prior DUI convictions will most likely have to have an IID installed. This is intended to prevent potential DUIs in the future.