Ill. Admin. Code tit. 80 § 1110.90
Following the filing of a representation or decertification petition, the Board shall provide the employer with a notice that shall be posted, by the day after the employer receives the notice, on bulletin boards and other places where notices for employees in the bargaining unit are customarily posted, or in conspicuous places in the absence of a customary posting location. If the posting would occur during a seasonal break or other period when a substantial number of bargaining unit members are not working, notice shall be provided to bargaining unit members through alternative means agreed to by the parties and the Executive Director or Board agent. If the parties and the Executive Director or Board agent are not able to agree on the alternative means of posting, the Executive Director or Board agent shall determine the alternative means of posting. In the case of majority interest petitions, the notice shall be posted for at least 21 days.
Ill. Admin. Code tit. 80, § 1110.90