I know it's different in every state, even hospital to hospital, or day to day, but my son has been put on 4 involuntary holds in the past 8 months - and he has never been violent towards others or threatening to harm himself.
What he has been is gravely disabled, unable to protect himself from harm and incapable of providing consent for treatment.
I've been told that you should know your state's laws, be able to quote it to the person doing the screening (so far, I haven't had to do this), and if needed, take names, etc and tell them that if the person in questions meets harm or does harm you will hold them responsible.
3 of the holds were around 2 weeks, the last one was only 1 week.
This is our law in Virginia - I'll try to bold the parts that have applied to him.
the person (i) has a mental illness and that there exists a substantial likelihood that, as a result of mental illness, the person will, in the near future, (a) cause serious physical harm to himself or others as evidenced by recent behavior causing, attempting, or threatening harm and other relevant information, if any, or (b)
suffer serious harm due to his lack of capacity to protect himself from harm or to provide for his basic human needs; (ii) is in need of hospitalization or treatment; and (iii) is unwilling to volunteer or incapable of volunteering for hospitalization or treatment.
The first 3 times, he asked to go to the hospital after he stayed awake for 5 or so days straight - then wanted to leave. He was presenting so out of it that they would think drug overdose at first.
The last time, he went 8 days without sleeping more than about 16 hours total and kept wandering into traffic - once in a busy parking lot, once just in our neighborhood, but the police were called twice. Both times, the police would ask me if they could help and were very nice to him, but they did not volunteer to transport or do the TDO even though they recognized that it was a mental health problem. I was OK with that - last think I want him to do is be afraid every time he sees an officer.