An ignition interlock device is a breathalyzer device that is hooked to your vehicle and requires you to breath into it before starting your vehicle. If your blood alcohol content (BAC) is above a pre-set threshold (usually at .04), then your vehicle will not start.

An ignition interlock device can be ordered by the court, or can be incorporated into a plea agreement. Often, this device is required if your driver's license is revoked or suspended due to a DPS hearing or DUI conviction.

In some cases, driving can be limited to work or medical treatment facilities. However, a driving interlock device can only be used in conjunction with a Class D driver's license. If you have a Class A, Class B, or Class C driver's license, your driver's privileges will be revoked with a DUI conviction or if you lose at a DPS hearing. An ignition interlock device (or any other work permit or temporary license) is not available to people with commercial licenses, including truck drivers, mailmen, chauffeurs, and other driver's requiring a commercial driver's license.