An ignition interlock device (IID) is a breath alcohol measuring device that is connected to your motor vehicle ignition.  In order to start the vehicle, a driver must blow a breath sample into the device which then measures alcohol concentration.  If the alcohol concentration exceeds the startup set point on the interlock device, the vehicle will not start.  You also need to blow into the IID periodically while you drive the vehicle.

Under Missouri law, a court may require that any person who is found guilty of or pleads guilty to a first DWI or Excessive BAC offense.  A court shall require that any person who is found guilty of or pleads guilty to a second or subsequent DWI / Excessive BAC offense shall not operate any motor vehicle unless that vehicle is equipped with an ignition interlock device for a period of not less than six months from the date of reinstatement of the person’s driver’s license.  In addition, any court authorized to grant a limited driving privilege to any person who is found guilty of or pleads guilty to a second or subsequent DWI / Excessive BAC offense shall require the use of an ignition interlock device on all vehicles operated by the person as a required condition of the limited driving privilege.

Talk to a Missouri DWI lawyer about whether this requirement applies to your situation.