The embryonic development is quite adaptive to environmental
humidity, between 40%-70%. However, high temperature accompanied
with high humidity should be absolutely avoided, because of
which will cause embryo death due to suffocation and overheat.
Appropriate humidity can help the embryo to be warmed evenly at
the early incubation stage, and to give off heat at the late
incubation stage. Furthermore, during hatching stage, the
chemical reaction between water and carbon dioxide will make the
egg shell crisp, which could help the poult pip out. During
incubation, low humidity cause quick evaporation of the water in
the egg, so as to cause excessive dehydration. This result will
lead to the sticking between embryo and egg shell if not so
serious. A more serious case can lead to embryo death due to the
dry chorionic membrane of the allantois which obstructs
assimilation of oxygen and exportation of metabolic waste. On
the contrary, high humidity will obstruct the evaporation of the
water in the egg, which make t