210 ILCS 95/18
The Director shall make findings of fact in such hearing, and the Director shall render his decision within 30 days after the termination of the hearing, unless additional time is required by him for a proper disposition of the matter. When the hearing has been conducted by a Hearing Officer, the Director shall review the record before rendering a decision. It shall be the duty of the Director to forward a copy of his decision, by registered or certified mail, to the owner, operator, licensee, permit holder or applicant, as the case may be, within 5 days of rendition of such decision. Technical errors in the proceeding before the Director or Hearing Officer or their failure to observe the technical rules of evidence shall not be grounds for the reversal of any administrative decision unless it appears to the court that such error or failure materially affects the rights of any party and results in substantial injustice to him.
210 ILCS 95/18