What is the physiological reasoning for lockdown? I have read that on Day 18, stop turning, raise humidity, and don't open incubator, which I have done. I have also read in other places that you don't need to raise humidity until you see first pip. Purpose of raising humidity is to prevent shrink wrap, which I understand. Makes sense that raising humidity at first pip (perhaps by tube in vent rather than opening incubator) would be ok. No rushes of cold air. I understand not opening incubator after pipping has started. That being said, I have lost fully developed chicks on every hatch I've had so far. I think I have been too cautious with the temperature and keeping it just a little too low, so that is one correction I've made. But I feel like if I understood the physiological reason for lockdown a little more, maybe I could trouble shoot more. Another thought I had was about ventilation... especially when you don't open the incubator for several days in a row. Are they using up their oxygen? I have only one vent on my incubator and I keep it open. Thanks!!