Over the years I've had my ups and down with hatching, using a variety of different incubators and have had some great hatches...and some dismal ones. A few months ago, I built a new incubator and hatcher and the first several hatches were near 100%. Over the next 6 - 8 hatches, the hatch rate has steadily declined even though everything is exactly as it was in the beginning. The lightbulb finally went on yesterday as to the possibly reason for my poor hatches. First, the eggs are incuabted in a separate bator and at day 18 I put them in the hatcher. The incubator has eggs in it most of the time, so I really haven't cleaned it much. The hatcher, however is given a thorough cleaning after each hatch and I have used some pretty strong bleach water to clean it. I realized that for the last several hatches (poor hatches) I have cleaned the hatcher JUST before putting the eggs in. I spray the inside, wipe it down, dunk the trays in bleach water and let them dry without rinsing. Don't know why in the world I never thought of it before now...but I am so sure that the chlorine is releasing chlorine gas inside the hatcher and the chicks are dying somewhere between day 18 and day 20. No more bleach solution for me! I will use a mild oxine solution and clean it a minimum of 3 days before the hatch, leaving the door open to allow the chlorine to be chelated by the circulating 02 in the air. I've always heard to be sure to use a strong bleach solution to "scrub the incubator (hatcher) in between hatches" and I believe that, for me, this has led to late chick death. Thoughts??