Large air sacs are great Jan. I don't actually know what happens if the humidity is so low that you end up with a huge air sac. Perhaps the chick dries out? Not a problem I have encountered. Even running the incubator dry in the UK the ambient humidity isn't low enough to give any problems -or at least none reported on the forums. Down here it may be completely different. The ambient humidity can drop to 20% with air from North Africa- you should see how much the apparently 'dry' wooden coops I brought over from the UK shrank when we got here!
First problem has come up. One of the chicks has one (!!!) splayed/spraddle leg. Got the legs attached to each other, but it keeps falling over uncerimoniously to the side of the good leg and has trouble standing. Any recommendations? How long should I leave the device on?
Just to finish this thread off, chicks are doing well. 4 out of 5 of the ones that I thought would hatch hatched in the end. The one that didn't was in a rather "long" egg, so very likely badly positioned for hatching. Two of the four had very slightly splayed legs (one corrected itself within 24 hours, the other is in a tape device which is holding the legs together), while the other two are happily bouncing all over the place.
A very sweet picture as well KittyKat. I read that overly long eggs shouldn't be used for hatching. Can't remember where? All our Wyandottes lay overly long eggs though and that's what they were hatched from. Perhaps the egg developed a double air sac?