The Illinois Secretary of State has an information page on monitoring device driving permits

All first offenders are entitled to a monitoring device driving permit (MDDP) as long as their license was not otherwise suspended.  That permit allows you to take your vehicle a certified technician for the installation of a breath alcohol ignition interlock device (BAIID).  This device prevents your car from starting unless you blow into a breathalyzer machine that registers a breath alcohol content of less than 0.05.

You may drive your car twenty-four hours a day, seven days a week, anywhere in the state.  You may also drive any other car that has a BAIID installed.  If you are caught driving a car without a BAIID you will be charged with driving on a suspended license.  If you drive a vehicle for work you may be eligible for an exemption for the purpose of driving work related vehicles.