This parameter is crucial for the quality of incubation. Humidity is normally used corresponding to a relative humidity of 57 to 60%.

The aim is to provoke at the beginning of incubation moisture saturation so that the egg does not lose too much water. As the incubation progresses, the egg evaporates part of the contents of this, to lose, on average, 11.5% of the original weight of the egg. This also depends on the thickness of the shell and under it; it will be given more or less moisture.

At the end of the incubation process is necessary to raise the humidity to facilitate softening of the shell membranes and thereby its package.

So, in the last days of incubation, when the water reserves in the egg have been exhausted, it is necessary to raise the humidity in the cabinet to prevent the drying of the shell membranes and the downy chicks hatching phase.

In the following table information relating to this issue is shown.

 

Species Hen	1st Incubation step (first 18 days).	2nd Incubation step (last 3 days)
Daily water loss (%)	0,5-0,6 %	0,7-0,8 %
Required relative humidity (%)	55-60 %	70-75 %

 

The minimum humidity limit for the wet thermometer should be 26.6 ° C and the maximum 35 ° C.