How long does it take for partial suspension hanging to cause complete brain death?

[Comatose11]

Most sources I've found either quote when brain damage starts to occur or long drop hanging. I'm looking for complete brain death with partial suspension hanging. I want to know how much time I need to make sure goes without being found in time. It seems like a very peaceful method, I just need to eliminate being found in time.

 

[Revan]

Most of what I have read puts it around the 20-30 minute mark.