Air sac smaller than it should be and broiler chick doesn't look like it's fully developed for a day 18 chick


Jun 19, 2022
Hello, good day to everyone! We've been gathering answers in the forums to see how we should handle our chick. We are first timers in incubating and hatching eggs. Eight months ago, our brother had to take care of three broiler chicks for a school project. We chose to keep them as pets. Unfortunately, our female chickens died recently and we only have the male chicken left. Due to this incident, we decided to incubate and hatch the eggs of our female chickens to keep their legacy. We have made a list of concerns and we are hoping we will get answers and help from the community! We also provided general details of the eggs and the situation:

The incubation process of the eggs started on June 1, at 5pm. We started with 4 eggs, but 3 of them are unfertilized. The only egg left is on day 18 and we see signs of movement. However, the air cell is too small and it seems the chick has slow development.​
The size of the air cell is between the size of a day 14 air cell and day 18 air cell based on this thread [].​
The size of the chick is around the size of a day 13 chick. We used this thread as a reference for the chick size [] If we got the sizes wrong, please feel free to correct us so we will know the real progress of our chick!
For the first 12 days of the eggs we placed them in a metal container [6 inch diameter] and put them on top of our UPS since we didn't have an incubator yet and we had to order it online. A UPS [uninterruptible power supply] can run a computer or device for a short amount of time when there is a power outage. We put thin foam between the metal container and the UPS so the eggs won't be subjected to higher temperatures. The UPS had a temperature range of 99.5-101.3 and we didn't turn it off. The temperature of the eggs around this time ranged from 37.5-37.9 Our incubation process was similar to still air incubation since we did not put water in the metal container. We did not close the container completely so there will still be ventilation.​

Our incubator arrived on June 12. We set it up and transferred the eggs around 12am on June 13. The incubator includes a temperature checker, heater, 2 water bags, spray bottle, and quilt. The size of the incubator is 31[L]x20[W]x20[H]cm. We don't have a hygrometer yet. The incubator doesn't have a humidity checker. We searched for a hygrometer in the three towns that we went to, but we didn't find any store selling one. All of the stores just don't sell hygrometers or they were phased out. The hygrometer we ordered online will arrive hopefully on June 20-21.​
We followed the instructions in the manual. We filled the water bag and laid the water bag flat on the heater. The height of "water" was around 5 cm as indicated in the manual. Unfortunately, we also sprayed water on the eggs since we saw one YouTube tutorial spraying water on his chicken eggs. We feel this was a terrible mistake which led to the small air cell size of the egg. We sprayed water on the eggs 5 times maximum and stopped when we read in the forums the importance of humidity and air cell sizes.​



The air cell of the egg is between the range of day 14 and day 18. We read in the forums that it's best to delay the lockdown and let the air cell grow bigger, bump the humidity up once there is external pipping. The size of the air cell increased after we added rice and silica gel in the incubator surrounding the egg on June 17. We also removed half of the water in the bag yesterday [June 19, 1pm]. We did not remove all of the water since we are worried the humidity will become too low at a very fast rate and we don't have a hygrometer yet. We provided photos of the egg so the development of the chick and air cell can be seen. Should we wait for the air cell to increase and observe until we see a fully developed chick (chick occupying majority of the space other than the air cell) before doing lockdown? What more can we do to increase the size of the air cell and aid the development of our chick?

How long can we safely delay the lockdown period and when can we start it based on the development of our chick? We read in one of the threads that one owner was able to hatch chicken eggs on day 26.

What's the proper placement of the egg for hatching? Should the lower end of the air cell be facing upwards, downwards or sideways if it were laying on its side? Should we lay the egg sideways or upright in a container [egg carton]?

Should we make a safety hole if there is no external pipping after 24 hours of the first sight of internal pipping? What situations require a safety hole for the chick and how can we do it if it is crucial in the survival of the chick?

What should be the humidity range and temperature for the lockdown period?

Should we stop turning the egg or do we continue to turn the egg until we see its air cell is at the right size and that the chick is fully developed? We have turned them 2-3 times a day [3 times mostly] since day 1.

We thank everyone in advance who will read our post and answer our questions! We really want our chick to live
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The makeshift Bator was set on a UPS...what is a UPS?

I would never spray an egg with water.

Air cells don't get huge until the day before hatch.

Not keeping the temperature stable can be a serious issue.
So can the temperature getting too hot.

I do not raise the humidity in my incubator until I see an external pip. I have excellent hatch rates.

I find that most people keep their humidity too high from the get-go and it causes problems too so if you do not have a humidity gauge it is possible your humidity has been too high to begin with. 8 keep my humidity level near 30 throughout and only raise it to about 50 for hatch day.

Turning the eggs is more important the first two weeks than the last few days.

Thank you very much for the responses! We edited the post and included what UPS stands for to avoid confusion. UPS means Uninterruptible Power Supply. We get thunderstorms here often which causes power outages. Sometimes, the electric company will do rotational brownout when there's a power shortage. We bought the UPS so our computer can last for 5-10 mins which gives us enough time to save the files we are working on during a power outage.

We plugged the incubator to the UPS so the incubator can still operate for 3 hours without electricity. The UPS was the only thing in our house that can provide heat for the chick and operate safely 24/7.

What do you guys think about the development of the chick and the air cell? We just checked the egg and it's still moving. We listed all the concerns we could think of so if we will encounter such problems, we already have the answers. Thank you very much!

Air cell marks video link:

Candled egg video link:
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