Incubator Humidity for Chicken Eggs — The Ultimate Guide

Incubator humidity is one of the crucial factors for the successful hatching of chickens. From placing newly hatched fertilized chicken eggs in the incubator until the chicks’ beaks pip through their shells, humidity levels determine their development. Simply put humidity in the incubator is so important that it’s the difference between new chicks and eggs.

Hatching eggs in an incubator

Of course, other factors like turning the eggs and the correct incubation temperature are also vital aspects of chicken development during the incubation process. However, ensuring humidity remains between 50 and 60 percent for the first 18 days will maximize hatch rate success.

In this article, you will learn all you need to know about incubator humidity for chicken eggs. You will also find out how to achieve ideal incubator humidity for hatching chicken eggs

What Is Humidity?

Humidity is the level of water vapor present in the air. In an incubator, humidity is relative to the temperature. Therefore, the correct incubation humidity is only possible if the temperature is set to 99.5°F (37.5°C) before adjusting humidity levels. Humidity is important because too much or too little incubation humidity impacts egg development. 

It’s vital to remember that humidity levels in a chicken egg incubator depend on the temperature. For example, increasing the incubator temperature without adding more water can cause humidity levels to drop. This is why relative humidity in the egg incubation period is so crucial. 

What Is Relative Humidity?

Relative humidity (RH) is the percentage of water vapor present in the air relative to the amount that could be absorbed at that temperature. Because warm air can hold more moisture (water vapor), relative humidity will be lower than the same humidity level in cold air. Therefore, humidity levels are relative to the incubator’s temperature. 

Here’s an example to help you understand the importance of relative incubation humidity for hatching chicken eggs. 

Let’s say the temperature inside the incubator is 100°F (37.8°C), and the relative humidity is 50 percent. If the temperature drops without adding water, relative humidity will increase. This is because cooler air cannot hold as much water vapor. 

Why Is Humidity Important for Successful Hatching of Chickens?

Humidity is vital for the hatching process to prevent unnecessary egg moisture loss. During the stages of incubation, an egg should lose around 0.6 percent of moisture per day. This equates to 12 to 14 percent of moisture during the incubation time.

Proper humidity levels allow the chick embryo to develop in the egg. As excess moisture evaporates, the developing chick has room to grow and has enough air. If the relative humidity is too low, the moisture evaporation will be too much, and the embryo will die. However, RH over 60 percent will negatively impact the chick’s development.

The loss of moisture also affects egg weight. Therefore, an egg will typically lose around 0.35 oz. (10 grams) through the entire incubation period. 

However, high humidity during hatching is vital during the hatching process. This requires setting the incubator’s relative humidity to around 70 percent. The humidity increase allows chicks to break out of their shells easier. 

Experts often attribute poor hatch rates to excessive humidity during the early stages of incubation and insufficient levels during the final three days, commonly known as “lock-down.”

How Do You Measure Humidity During Incubation?

Two methods of monitoring proper incubation humidity are a hygrometer or wet-bulb thermometer. In addition, some incubators have an inbuilt thermometer and hygrometer to show moisture levels during incubation. 

The Pennsylvania State University says it’s straightforward to create a wet-bulb thermometer. You add a cotton wick to the end of a regular incubator thermometer with the other end in water. As the water evaporates, it cools the temperature on the wet-bulb thermometer. The greater the difference between the dry-bulb thermometer and the wet bulb represents lower relative humidity. 

Here is an example:

  • Dry bulb – 100°F, wet-bulb – 83.3°F, relative humidity is 50%
  • Dry bulb – 100°F, wet-bulb – 90.7°F, relative humidity is 70%

It is also possible to measure proper incubation humidity for hatching eggs by weighing them daily. According to experts, chicken eggs lose 12 to 14 percent of their weight during the 21-day incubation period. 

How to Achieve the Correct Humidity Levels

Incubator Humidity

Maintaining the correct humidity levels during incubation is essential for successful hatching. Suppose the humidity is too high or too low. In that case, it can affect the weight loss of the egg and ultimately lead to unsuccessful hatching. Unfortunately, not everyone has access to a reliable hygrometer to measure the humidity levels in their incubator accurately. However, there are still ways to achieve the correct humidity levels without one.

One way to do this is by periodically weighing your eggs throughout incubation. Most bird species will need to lose between 13 and 15% of their weight from the first day of incubation until they hatch. By weighing your eggs every few days, you can adjust the humidity accordingly if there is too much or too little weight loss. This method may be more time-consuming than using a hygrometer. Still, it is an effective way to ensure that your eggs receive the right amount of moisture during incubation.

It is good to remember that increasing humidity in an incubator requires a large surface area. For example, placing a wet sponge in the incubator is more effective at raising humidity than a cup of water.

What Should the Humidity Levels Be for the 21 Days of Incubation?

A high-quality incubator is crucial for increasing the chances of a successful hatch. For example, an automatic incubator turns the eggs regularly, maintains an even temperature, and controls relative humidity. Forced-air incubators use a fan to keep the air moving and provide oxygen. However, cheaper still-air incubators use air vents to circulate air. 

Regardless of the type of incubator you use, you must monitor humidity for successful incubation.

Here are some guidelines for humidity and temperature levels for the 21-day incubation period:

  • Temperature range: 99°F to 102°F (optimal temperature is 100.5°F)
  • Relative humidity day 1 to 17: 50 to 55 percent
  • Relative humidity day 18 to 21: 70 to 75 percent

To adjust the humidity in the incubator, you should follow the manufacturer’s instructions. But remember that it’s easy to increase incubator humidity—it’s not so easy to reduce it.

If Humidity Is Too Low

Inadequate humidity in the incubator causes the eggs to lose excessive moisture. This results in an increased air space inside the egg. Additionally, the chick sticks to the egg and cannot develop properly. Therefore, if the air space is too large, the chicks will develop below average and be too small.

Unfortunately, small chicks often lack the strength to hatch on their own. This often causes death before or shortly after hatching.

If Humidity Is Too High

Humidity that is too high during incubation causes serious problems for the developing chick.

High relative humidity levels cause the chick to grow too large in the shell. This results in a smaller than normal air space. The lack of space restricts movement in the egg, meaning the chick cannot get into the right position to pip the shell. It will also lack sufficient oxygen to get out of the shell.

Reasons Why the Incubator Humidity May Be Changing

Maintaining property relative humidity for hatching eggs can be challenging, especially for first-time chicken owners. Even with incubators that do most of the work for you, certain factors can affect humidity levels.  

Two crucial factors that impact incubation humidity are the following:

  1. Water surface area: A larger surface area inside the incubator results in more humidity. In this case, the depth of water doesn’t affect humidity levels. Instead, it is how much water can evaporate. Most incubators have water channels and trays to keep the right percentage of vapor in the air. Additionally, you can use evaporating blocks or pads.
  2. Ventilation: The amount of fresh air entering the incubator also impacts relative humidity. For example, reducing ventilation helps to increase humidity. On the other hand, increasing airflow decreases the percentage of relative humidity. 

However, there are external factors that could be causing changes to humidity levels in the incubator. Here are a few to check:

Chicken Hatching Day 21
  • Room temperatures affect humidity levels inside the incubator. Therefore, ensure the incubator is in a room with an even temperature.
  • Open windows can cause drafts and affect the room temperature. 
  • The thermometer or thermostat could malfunction.
  • Inadequate air circulation causes low humidity levels.
  • It is difficult to increase humidity if the temperature is too low.
  • Too many eggs in the incubator can impact humidity.
  • Inadequate water in the tray can cause dry air in the incubator.

Humidity for Hatching Chicken Eggs

Incubation humidity must be around 70 percent for chicks to peck their way out of the shells. Most experts agree that 70 to 75 percent is the ideal level. However, some say that 65 percent is sufficient. However, you must increase humidity to the correct levels three days before hatching. 

How does higher humidity affect the hatching phase? The additional vapor in the air helps soften the eggshell, allowing the new chick to break free easily. Also, during the last three days of hatching, you should stop turning the eggs as the embryos are in position for hatching. 

Can I add water to the incubator during hatching?

The best way to ensure hatch success is to add enough water three days before hatching time. However, if humidity levels drop below 65 percent during the hatching period, you can add more water as necessary. Most modern incubators have an additional channel to add water without lifting the lid. However, quickly lifting the lid to add water shouldn’t hurt the chicks. 

It’s good to remember that humidity will spike when a chick hatches. This is entirely normal, and the humidity levels should return to normal relatively quickly.

Incubation Humidity — In Conclusion

Humidity is a critical factor for the successful hatching of chicken eggs. Therefore, as the incubation process progresses, you must monitor relative humidity levels. Then three days before hatching—in other words, on day 18—you should increase humidity for hatching. If the humidity is too low or too high, it can lead to embryo development problems and reduced hatch rates.