Why don't pipped eggs hatch?

Since this issue seems to plague many of us and is just so disheartening, I have been searching for possible answers. At this point, I believe that I have determined the issue to be not enough ventilation. I have an Rcom Suro King and there is only one ventilation hole at the top and 4 very tiny ones in the bottom corners. I intend to change that today! At minimum, I am going to drill the 4 small bottom ones to make larger holes and will probably also drill 4 more on the top half somewhere. I know it can be difficult for some folks in dry climates to keep the humidity up, but if you sacrifice ventilation for humidity, you'll still have dead chicks. Also, wrapping incubators up in blankets during a power outage can cause the oxygen level to drop inside the incubator leading to embryonic death.

I have gathered information from various professional sources and some of the answers are below:

Mississipi State University

Pipped eggs that do not hatch

If chick embryos develop to the pipping stage, or at first shell cracking at hatching, they are normally healthy enough to hatch unless some incubator adjustment prevents it from happening. The problem is usually caused by either 1) poor ventilation or 2) improper humidity.

The air exchange requirement within an incubator is greatest during the last day of incubation. The chick embryo's oxygen requirement continually increases during development and especially when breathing using the respiratory system just before hatching. The vent openings are frequently restricted at this time in an attempt to boost incubator humidity. Instead of helping the chick hatch, the chick is suffocated from lack of ventilation. Never decrease ventilation openings at hatching in an attempt to increase humidity. Increase humidity by other methods. If any vent adjustments are made, they should be opened more.

Another reason for mortality during hatching is improper humidity adjustment. The deaths can be produced from too much humidity during the entire incubation period or from too little humidity during the hatching period.

The desired egg weight loss during incubation caused by water evaporation is about 12 percent. If humidity during incubation is kept too high, adequate water evaporation from the egg is prevented. The chick can drown in the water remaining in the shell at hatching. A dried coating around the chick's nostrils and beak indicates that drowning was likely. Attention to maintaining proper incubation humidity during incubation will reduce the potential for this problem at hatching time.

If the humidity is allowed to decrease after the chick pips the shell, the membranes within the shell can dry-out and stick to the chick. This prevents the chick from turning inside the shell and stops the hatching process. The chick eventually dies. If the membranes around the shell opening appear dried and shrunken, the cause is probably low humidity during hatching. This condition can occur quickly (within 1 or 2 minutes) when the incubator is opened to remove or assist other chicks that are hatching. When hatching begins and proper incubator conditions are attained, the incubator should never be opened until after all chicks are hatched and ready for placement in the brooder.


University of Illinois Champagne

HOW THE CHICK EMERGES FROM THE SHELL
The head of the chick develops at the large end of the egg. Between the 15th and 16th days, the chick orients itself so that its head is near the air cell at the large end of the egg. Not long before the chick is ready to attempt to make its way out of the shell its neck acquires a double bend so that its beak is under its right wing and pointed toward the air cell. About the 19th day the chick thrusts its head forward. Its beak quickly breaks through the inner shell membrane, and the chick's lungs begin to function. Complete breathing by the lungs usually does not occur until the 20th day of incubation.
Using its egg tooth (a tiny, sharp, horny projection on the end of its beak), the chick pecks at the shell thousands of times. Finally, the young bird pips its way through the shell and begins to breathe air directly from the outside. After the chick has made a hole in the shell, it stops pipping for three to eight hours and rests. During this time, it is acclimating its lungs to the outside atmosphere. After the resting stage is completed, the second stage of pipping begins.
The chick begins to turn slowly inside the egg. As it turns, usually counter-clockwise, the cutting edge of the chick tooth continues to chip away. In two to five hours, the chick has made about three quarters of a turn inside the egg. As the chick progresses in its movement around the shell, it begins pushing on the egg cap (large end). Squirming and struggling, the chick works feverishly for about 40 minutes pushing at the cap. Finally with a vigorous shove, the chick breaks free from the shell, still wet and panting.

VENTILATION
Proper ventilation is very important during the incubation process. While the embryo is developing, oxygen enters the egg through the shell, and carbon dioxide escapes in the same manner. As the chicks begin to hatch, it is essential that they receive an increasing supply of oxygen. This means that the air openings need to be opened gradually to increase the flow of air.

Small Farm Permaculture
Ventilation Requirements for Hatching Chickens

Embryos inside incubating eggs need oxygen which they get via their shell from the air around them. For this reason, it is important to ensure adequate ventilation by maintaining the patency of the ventilation holes in your incubator.
As they develop, the amount of oxygen needed increases. In larger incubators, this is the time to gradually open the adjustable vents till they are set on fully open by hatching time.

However, at pipping time higher humidity is also needed which is hard to achieve if air flow is too high. Thus a balance between the two must be aimed for.

 

I have always wondered why I had better hatches in my homemade "Miss Prissy" bator and now I think I know. I had eight 1/2" holes drilled all around, top and bottom for ventilation. I wrongly assumed that by buying a nice incubator everything would be perfect...and in some ways it is better for sure. But it is obvious that there is not enough ventilation for an incubator full of pipped and hatched eggs. Who knows, maybe this is one of the causes of quitters during incubation as well.