Open. I've never used this incubator with the vent hole closed. It's positioned just above the fan, so it's constantly having air drawn in. No issues with stable humidity at all. The innermost tray filled will keep the incubator in 30 to 35 range. Middle tray keeps it at about 40. Exterior tray...
It's just easier to disinfect it thoroughly if you unscrew the screen. You don't want that fluff getting up into the heating elements. And you can get the fan cleaned up a bit while you've got it exposed.
Normal for post hatch. Just a preview of how much down, dust, and dander those chicks can produce. If you think that's bad, just you wait till they start feathering in. Unscrew, blow out the debris, and disinfect.
More info needed. Shipped eggs or local? Humidity? It can take a lot of practice to get really good, consistent hatches. And there a lot of things that can go wrong along the way.
The issue with keeping the turning tray in is a safety concern. Chicks can get stuck, legs can get wedged, it's just not a good idea to leave it in. Remove ASAP. A few minutes is not going to hurt anything.
Adjust the set temp down by a degree. If they hatch a day early, than you know your temp is still a bit high. Lower it another half a degree for your next batch of eggs. If they hatch a day late, than the incuview temp was correct, and you can adjust it back for your next hatch. Better to lower...
Directly from the instructions that came with a replacement IncuTherm unit -
Set Temp :
This will move the temperature up and down by 0.1 degree increments. If you hold the UP or DOWN buttons down, it will change more rapidly. NOTE: the temperature sensor on this device is very sensitive and...