to much and the airsack is to small. to dry and they find it very hard to break out. some say to use water others say you don't i try to aim in the 50-60% range. all you can do is experiment until you get a good hatch rate. each machine and room its in are diffrent get a hydromiter and stick it in. don't trust the room humidity to be the same as the incubator. we have had 80+ outside and 30 in the machine.