Ideal Humidity for Incubating Chicken Eggs

Chicken eggs need to lose a certain amount of moisture for the proper development and hatching. The relative humidity inside an egg incubator controls the moisture loss inside the egg. Chicks require proper humidity in your egg incubator and getting the humidity right for a successful hatch need not be a challenge. At the start, you must keep about 55% humidity levels, then increase to 65% once piping occurs in the last three days.

To achieve successful incubation and hatching, this guide explains egg humidity requirements. You’ll also learn how to measure incubator humidity correctly and how to maintain the correct humidity levels throughout the entire incubation and hatching process.

What is Humidity?

Humidity is simply the amount of water vapor present in the air. What we usually measure is the percentage of relative humidity. This is the actual amount of water vapor relative to the air temperature and the maximum amount of vapor the air could hold at this temperature. In general, hot air can hold more water vapor.

Thus, as the relative humidity decreases, the moisture from the egg evaporates faster so that it loses more moisture. Conversely, as the relative humidity inside the incubator increases, the moisture from the egg evaporates slower so that it does not dry out. 

The relative humidity can be measured using an electronic hygrometer that provides a digital reading of humidity inside the incubator. However, there may be a small margin of error if you don’t calibrate it.

You may also measure the humidity using a pair of thermometers that provide wet and dry buld measurements. One thermometer measures the air (dry-bulb) temperature, while the other thermometer measures the (wet-bulb) temperature around the bulb of the thermometer with a cotton wick dipped into a container of water.

Do You Need Humidity in Hatching Chicken Eggs?

Humidity provides moisture for the eggs. Embryo development requires oxygen that comes through the porous egg shell. Moisture evaporates from the egg, which loses some of its weight in the incubation process. As the egg loses weight, the air sac becomes bigger. 

To get enough oxygen for hatching eggs, theyneed to lose the right amount of moisture during incubation. At this point, the chick should be the right size before it then breaks through to the air sac to breathe. To do so, it needs both the humidity and ventilation at the right level. With the right combination of humidity and air circulation, the eggs get the oxygen they need for embryo development and successful hatching.

Ideal Temperature and Relative Humidity for Incubating Eggs

The recommended temperature for hatching eggs is between 99°F 100°F (or between 37.5°C and 37.8°C). Maintaining this range of temperatures increases the chances for the proper development of the chicks during the hatching process. 

As mentioned, humidity is also critical for the development of the chicken eggs. The incubation period of chicken eggs lasts 21 days. During the first 18 to 19 days, you must keep the humidity levels around 45% to 55% to improve the embryo development. In the last three days, you need to increase the humidity by about 20%. 

Starting at Day 19, you should maintain the humidity at around 65% for the development of the egg before hatching. The increase in the humidity provides enough moisture to soften the eggshells for the chicks to break out easily. You need to maintain this humidity until the eggs hatch.

How to Control Humidity in an Incubator

The first step in controlling the moisture levels in an incubator is by using a hygrometer to monitor the humidity. A hygrometer is an essential tool you will need to monitor and maintain the right humidity for hatching. 

You need not measure humidity immediately after installing the incubator for the first time. First, prepare the incubator to get a stable temperature and humidity level before measurement. If you’re installing a store bought incubator, follow the instructions indicated for your specific model. Some incubators may come with a built-in thermometer and hygrometer for your greater convenience.

For a forced-air incubator or those with a fan inside, set the temperature at 100°F and allow the temperature to stabilize after a few minutes. If you’re using a still air incubator (models without a fan), set the initial temperature at 102°F. Note that this is only the initial temperature, and it can change after a few minutes before you measure the levels of humidity inside the incubator.

When the temperature stabilizes at around 99°F to 100°F, take your hygrometer and measure the humidity in the incubator. The humidity should be at least 60% in the beginning. Once the humidity level stabilizes at around 55%, you can now start putting eggs inside the incubator.

Monitor both temperatures and humidity levels and compare them with a separate device to account for small inaccuracies. If you use a wet-bulb thermometer, you should be able to read 85°F to 87°F with the 100°F dry temperature, which is equivalent to 55% to 60% humidity in standard measurements.

You must incubate eggs within this range of humidity levels, until the last three days of incubation when they need a little more moisture. This is a crucial factor to your eggs hatching properly at the right time. Once you have the temperatures stable, controlling humidity levels inside the incubator mostly depends on the water source and air circulation. Whether you need to increase or decrease the humidity, the most effective way to do so is to either add or remove water. You may also need to reduce or increase the ventilation to provide the right levels of airflow.

Fluctuations in temperature should be more of your concern than small variations in humidity over the period of incubation. What you need to optimize is the average humidity for the entire 21 days to achieve proper development of the chicks.

How to Control Humidity in an Incubator

What happens if the humidity is too low in an incubator?

An incubator for chicken eggs has particular requirements for humidity levels. In case the humidity drops below the ideal range of 50% to 55%, the eggs will lack moisture, which usually leads to the development of small chicks. 

When humidity is too low, the eggs lose too much moisture to the dry air. This results in a bigger air sac and a smaller chick. With the right humidity, chicken eggs must lose 13% to 14% of their weight from the beginning of the incubation period. You can also monitor the size of the air sac by candling eggs.

While the lack of humidity does pose some issues for the overall development of little chicks, it’s usually not that big a deal as opposed to excess humidity. The larger air space leads to smaller chicks, but the health in general will not be affected as much. In the case of high humidity, the eggs may lack air and lead to respiratory problems, which we’ll talk about a bit later.

Although short term changes are not a big concern, it’s best to maintain proper levels of humidity and temperature in an incubator. In case you experience extreme weather changes during the incubation period, make sure to check the levels regularly to monitor any change, especially during the last three days when hatching should occur.

How to Increase Humidity in an Incubator

As mentioned briefly, you can control the humidity inside the incubator by adding or removing the water source and ventilation. The easiest way you can raise the humidity in an incubator is by placing water in a wide, shallow container inside. This is a more permanent solution to increase the humidity level in an incubator. 

But if you want to increase the humidity instantly, there is a quicker solution by spraying a small amount of water into the ventilating holes of the incubator. This increases the moisture levels for the eggs. Remember to use warm water so as not to affect the incubator temperature. Some manufacturers use an incubator sponge or absorption pad to increase the surface area of the water, while a few others include a humidifier with a heater that evaporates water into steam.

Reducing ventilation also helps maintain the right humidity inside the incubator. Eggs need the air and the right amount of moisture for embryo development. But too much air from outside can change the humidity levels inside. To maintain high humidity in the incubator, you must keep the moisture inside. You need the right combination of humidity and ventilation to circulate the moisture the eggs need to soften and the air that the developing chick needs to breathe.

What if the humidity is too high in the incubator?

Excessive humidity is often more risky for the eggs in your incubator. If the humidity reaches above 65% or 75% during the last three days, the eggs dry out more slowly and lose too little moisture. This results in a smaller air sac and a larger chick. When humidity is too high, the air space becomes too little and we get a large chick unable to breathe and crack its shell to go out.

Larger chicks may have trouble moving into their correct hatching position. In case they do manage to get in position, the membrane may become too thick and rubbery to break through. If the chick breaks through the air sac, it would suffocate from lack of oxygen. 

If the humidity is too high, there is less moisture or weight loss, which could be harmful to the chick for the reasons above. Aside from monitoring the humidity levels, you can check the egg’s air sac to make sure the chick is developing properly with enough space to move and air to breathe once it hatches. 

How to Reduce Humidity in an Incubator 

In case there is too much humidity in your egg incubator, just do the opposite solutions to increasing humidity. The simplest way to reduce humidity in an incubator is to add ventilation. More air circulation reduces the amount of moisture in the air, allowing it to evaporate into the outside, decreasing the overall humidity. Another way to reduce humidity is to remove the water from the incubator. Excess water and air contributes to higher humidity levels.

However, if you live in a high-humidity area, simply opening ventilation to your incubators might add more humidity from the outside. In this case, it might be a good idea to keep your incubator in a room with less humidity or a more controlled environment to make incubator humidity control more accurate. 

Remember that ventilation plays a critical role in controlling the humidity in your incubator. Choosing the right ventilation system can change the overall development and hatching process of the chicken eggs. The right ventilation gives the embryos adequate amounts of oxygen for the healthy development of your little chicks. So if high humidity is a problem for you, it’s important that you pay attention to ventilation in your incubator.

How to Reduce Humidity in an Incubator 

Final Words

When first setting your chicken eggs in an incubator, you need humidity levels of around 55%. Then, three days before hatching, you must raise the humidity to about 65%. At this time, you also need to maintain the right temperature and keep at least a third of your ventilation open to provide enough airflow. After the first signs of pipping, the chicks need more air and moisture to break out at this final stage of hatching. 

Do not break the eggs yourself and simply try to keep the right humidity levels and air circulation during the process of hatching. Humidity levels play a critical role in this process, and getting them right can change the whole experience for you. Remember to check the humidity level, temperature, and ventilation regularly throughout the incubation period to have a higher success in hatching your chicken eggs.

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