I have only been into one shoot house in all of my shooting days.
They had a system like the old mines to tell if a person was still in there. There was a peg board with numbered tags. If a tag was not hanging on the board then some one was inside. There were more than one for group training. Though the group training was for LEO's only.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.