(a) The following persons may apply for admission to a public or private hospital or treatment resource for diagnosis, observation and treatment of a mental illness or serious emotional disturbance:

(1) A person who is sixteen (16) years of age or over and who does not lack capacity to apply under § 33-3-218;

(2) A parent, legal custodian, or legal guardian who is acting on behalf of a child;

(3) A conservator whom the appointing court has expressly granted authority to apply for the person's admission to a hospital or treatment resource for mental illness or serious emotional disturbance;

(4) A qualified mental health professional acting on the basis of the terms of the person's declaration for mental health treatment;

(5) A person's attorney in fact under a durable power of attorney for health care, under title 34, chapter 6, part 2;

(6) A caregiver under title 34, chapter 6, part 3, who is acting on behalf of a child; or

(7) An individual acting as an agent under the Tennessee Health Care Decisions Act, compiled in title 68, chapter 11, part 18 or an individual designated as a surrogate under § 68-11-1806(a).

(b) An individual's surrogate as designated under § 68-11-1806(c) may also apply for such admission provided no person may be admitted by a surrogate under this subsection (b) for more than twenty-one (21) consecutive days unless a petition has been filed pursuant to part 5 of this chapter, or unless an individual who meets any of the criteria set out in subdivisions (a)(1)-(7) of this section applies for voluntary admission subsequent to an application by a surrogate for voluntary admission under this section.