Involuntary commitment to psychiatric hospital?

I'm wondering when a person is evaluated by the county designated mental health professionals for involuntary admission to a psychiatric hospital or clinic, is the person taken right then and there if they are deemed a safety concern for themselves or others? This is an issue with an elderly person that has had many seizures recently and is not following medical guidelines (ie taking meds, not drinking, driving, etc.). Hoping this is a short term issues, but we're so concerned about him. He's being evaluated in an hour. Wondering what to expect.