I was maintaining my pool one day and it needed about 2 quarts of acid so I dumped it in. Little did I know that my wife, son and daughter had pulled up in the garage about 15 minutes later. My son, who has been told not to get in the pool without supervision, jumps in the pool and swims around. I had gone around the house and went in and was talking to my wife when my son walks up and is all wet. I said, "You did not get in the pool did you?". He said he did and I said I just dumped a bunch of acid in it. I asked if he was itchy or eyes hurt and he said they did not.
I am with Richard, 30 minutes should be plenty. I usually wait an hour for peace of mind. I don't recommend 15 minutes, like my story above, that was an accident.