I work Per Diem/contigent. I don't know what "per diem pool" means though...unless you mean extra staff that goes where they're needed.
I don't get benefits, though I make a few extra dollars an hour since I don't. (compared to fulltime/part time staff)
Also at my institution I have to work a minimum of two days a month. (I work once a week)
Also at my institution I have to work holidays/weekend's .... but it really depends what institution you're at.
The last hospital I worked at contigent would be first to get called off. (for economical reason's since they pay us more per hour) But where I currently work it goes by that.
And the floor I work at is staffed well as compared to the rest of the hospital. So that mean's we are constantly pulled to other floors. Since I only work once a week, I'm rarely on my "own" floor I'm pulled all over...