An alcohol ignition interlock device (IID) is a breath-test device that is connected to a vehicle’s ignition. A vehicle with an IID installed will not start unless the driver blows into the interlock and has a blood alcohol concentration (BAC) below a limit set by the court—usually .02 BAC. IIDs must be installed by a certified technician approved by the state’s department of motor vehicles (DMV). The IID will collect data (engine starts and stops, breath test results, and tampering attempts) and report it to the monitoring company, which will report it to the court.

IIDs reduce repeat offenses for DUI/DWI by approximately 70% when installed. Laws vary from state to state and courts have significant discretion, but a judge may order a person convicted of a first DUI/DWI offense to install an IID and will order a person convicted of a second or third DUI/DWI to install an IID. Courts will often order an IID installed on the defendant’s vehicle as a condition of bond (to be released from jail) and of probation (following jail or prison time, or in lieu of any or more jail or prison time). The court may order the defendant’s IID to remain on the vehicle for 1-3 years or more.

Despite these laws and programs, only about one-fifth of those arrested for DUI/DWI have an IID installed.

In Nevada, an alcohol ignition interlock device (IID) is a mechanism that prevents a vehicle from starting if the driver's breath alcohol concentration (BAC) is above a preset limit, typically .02 BAC. Nevada law mandates the use of IIDs for certain DUI offenses. As per Nevada Revised Statutes (NRS) 484C.400, individuals convicted of DUI may be required to install an IID in their vehicles. The requirement is mandatory for all offenders with a BAC of 0.18 or higher and for repeat offenders. For first-time offenders with a BAC below 0.18, the court has the discretion to order the installation of an IID. The duration for which the IID must be installed varies, with a minimum period typically being six months. The device must be installed by a state-approved technician, and the data collected by the IID is reported to the monitoring company and potentially to the court. The use of IIDs aims to reduce the likelihood of repeat DUI offenses and is often a condition for the offender's release from custody or probation.