92 Ill. Adm. Code 442.220
Defrosters
Section 442
Section 442.220 Defrosters
Defrosting equipment shall be
installed so as to help keep the window to the left of the driver and the glass
in the service door clear of fog or frost. This defrosting equipment shall
conform to those FMVSS 103 (49 CFR 571.103) performance requirements that are
applicable to school bus windshields.