I opened the incubator on my first hatch as a few of the chicks needed a bit of help; they were oversized and unable to turn around to zip after having pipped 24+ hours previously. I did so in the bathroom after a shower to raise the humidity and with the heat on. The humidity rose to nearly 90%, temp between 100 and 101 degrees. The remaining chicks were unaffected by my doing so and 2 of the 3 that needed help survived and are doing great. (No. 3 was just too weak and died.)
