An ignition interlock device is a breathalyzer installed in a driver's vehicle that measures the level of alcohol in the breath . Connected directly to your vehicle's ignition system,  you are required to blow into the attached mouthpiece to test your Breath Alcohol  Concentration (BrAC ). In the case, the alcohol concentration exceeds a specified legal level, the interlock device temporarily prevents your vehicle from starting.

All 50 states in the US have adopted laws that allow or require the installation of devices to prevent convicted DUI offenders from driving under the influence of alcohol. These ignition interlock laws vary widely from state to state.

Tennessee ignition interlock laws require all DUI offenders to install an interlock device.

* Offenders may be able to apply for limited driving privileges with the condition of interlock device installation, after completion of a minimum period of license revocation.

* The length of that period depends on the offenders conviction history, as does the overall length of the ignition interlock period.