405 ILCS 5/4-400

(a) A person 18 years of age or older may be admitted on an emergency basis to a facility under this Article if the facility director of the facility determines: (1) that he is a person with an intellectual disability; (2) that he is reasonably expected to inflict serious physical harm upon himself or another in the near future; and (3) that immediate admission is necessary to prevent such harm.

(b) Persons with a developmental disability under 18 years of age and persons with a developmental disability 18 years of age or over who are under guardianship or who are seeking admission on their own behalf may be admitted for emergency care under Section 4-311.