42 C.F.R. § 51.42
(b) A P&A system shall have reasonable unaccompanied access to public and private facilities and programs in the State which render care or treatment for individuals with mental illness, and to all areas of the facility which are used by residents or are accessible to residents. The P&A system shall have reasonable unaccompanied access to residents at all times necessary to conduct a full investigation of an incident of abuse or neglect. This authority shall include the opportunity to interview any facility service recipient, employee, or other persons, including the person thought to be the victim of such abuse, who might be reasonably believed by the system to have knowledge of the incident under investigation. Such access shall be afforded, upon request, by the P&A system when:
(c) In addition to access as prescribed in paragraph (b) of this section, a P&A system shall have reasonable unaccompanied access to facilities including all area which are used by residents, are accessible to residents, and to programs and their residents at reasonable times, which at a minimum shall include normal working hours and visiting hours. Residents include adults or minors who have legal guardians or conservators. P&A activities shall be conducted so as to minimize interference with facility programs, respect residents' privacy interests, and honor a resident's request to terminate an interview. This access is for the purpose of: