I hope you are right because I see some people saying the humidity inside of the incubator is effected by the humidity in the room.
It is effected by, but it's not dictated by... If you have low humidity in the house it will be harder to keep the humidity up in the incubator, and the reverse is true if you have high humidity in the house it will be easier to keep the humidity up, as the incubator is not air tight and thus there are air exchanges...
The last hatch I did, one chick peeped but never made it out. All I can say, I had given them too much humidity because I filled up both sides of the water pot the whole time from day 1 to day 21.
Sometimes they just don't make it... The absolute best way to verify the humidity is correct is to weigh the eggs and monitor gains and loses, but this is impractical for many, another good way is to monitor the airsack size and development by candling... But, inherently people are lazy, so over the years people have found that this or that percentage of average humidity works OK and just follow that guideline...
Remember in the wild a broody bird has pretty much no control over humidity, and they most certainly don't boost the humidity on the last three days... They can't count the days
nor do they have a means to control humidity, if it's 95 °and raining that day with 100% humidity so be it, they can't lower it to 50% humidity...
For those that say the room temperature should not drop bellow 70 F, A few days ago, it got cold in Maryland and my house temperature was 60 but my incubator still kept the temp at 99.5 all the time.
There are two types of incubators, ones that are thermostatically controlled and those that are teetering on a balance beam with no temperature control...
For ones that are teetering aka ones that have a heat light on 24/7 and temp is controlled by the number of holes you punch into the incubator so that the hot air inside mixes with the cooler air outside and mixes together at 99.5°... It's very important to maintain ambient air temps outside in these types, as that is part of the balancing act... For example the light bulb inside these type of incubators might raise the temp +30° after you punch in 20 holes, so if the outside temp is 70° that is pretty good, but if the outside temp is 80°+30° you have a bad day...
For those that are thermostatically controlled outside air temp is not nearly as important, or better stated as long as the outside air temp does not exceed 100° or fall below whatever temp that overwhelms the heater inside the incubator preventing it from getting to 99.5°... Basically don't put your incubator over a heat vent or on a sunny window sill or anywhere else that might exceed 100° and don't put it outside in an unheated shed during the winter and expect good results...
