Trigger shot before iui appointment

How long after Ovidrel trigger shot do you ovulate? I think I read that 36hrs is just an average and it could work as early as 24 or as late as 40hrs after injection. So a Dr would just guessing when they want me to schedule my IUI at 36hrs after trigger. I guess I'm concerned what if I do actually ovulate at 24hrs post trigger, my egg quality would be demenished or dead before the sperm were even put in. Just confused, if you've been through IUI please explain I would be so grateful!!💕💜🤦🏼‍♀️