How to control humidity in an incubator

Humidity and temperature are the two most important factors when it comes to hatching eggs in an incubator. Temperature can be controlled relatively straightforward, but humidity can be a bit more tricky. In this article I’ll show you how to control humidity in an incubator by telling you:

  • Why humidity in an incubator is important
  • What the humidity in an incubator should be
  • How you can adjust the level of humidity in an incubator
  • Some general tips and tricks
  • Where to place your incubator

In case you are short on time I would like to mention that nowadays there are great incubators on the market that include fully automatic humidity control. If you want to see a few, check out my best egg incubators article. If you do have the time, not buying automatic incubators and instead doing everything the old fashioned way definitely has its charm!

Why is humidity in an incubator important

When an egg is initially laid, the egg is full of various liquids, including some moisture. During the incubation process, the egg will slowly lose some of its moisture through the pores of the shell. The amount of moisture the egg loses depends on the outside humidity. When the egg loses some of its moisture an air cell will form inside the egg. That air cell is where the chick decides to hatch. If the air cell is too small, the chick might drown while pipping through the shell. If the air cell is too large, the membrane might end up being too small for the chick before the pipping process begins. When the size of the air cell is exactly right when the pipping process begins, the eggs have the biggest chance to hatch successfully.

Humidity and temperature meter

What should the humidity in an incubator be

Here is where it gets tricky. Unlike as with temperature, there is no perfect answer for the optimal humidity level in an incubator. It always depends on the embryo growth. There are however two important aspects. First off, the air cell should be about 13-14% of the total volume of the egg when the pipping process begins. Secondly, during the lockdown period the humidity should be a lot higher than before. Somewhere in the 55-75% range.

When it comes to the three weeks before the lockdown period, some chicken hatchers prefer to keep the humidity very low. Possibly as low as 25% (dry hatching). While others keep the humidity above 50% right from day one. Personally I’m more a fan of lower humidity levels during the first three weeks, but it is important to try out what works for you.

What you should do is candle the eggs every week to check on the development of the embryo and the air cell. After the first week the air cell should be about 4%, after the second about 9% and after the third about 13-14% of the total volume of the egg. If the air cells are too small you will need to lower the humidity. If the air cells are too big, you will need to raise the humidity a bit. Depending on how much too small or too big the air cells are, you should adjust the humidity by 5-15%.

How to adjust the level of humidity in an incubator

How to increase humidity in an incubator

The best way to get the humidity up in an incubator is to put more water in the incubator. If that isn’t enough, try to keep the incubator closed as much as possible. Every time you open the incubator some of the humid air gets out and is replaced by not so humid air. If neither of those are enough, you can add an extra petri dish of water somewhere in the incubator. This will result in more water evaporating, which increases the humidity a lot.

How to decrease humidity in an incubator

The easiest way to decrease humidity in an incubator is to simply open the air vents and remove water from the incubator. This is in almost all cases more than enough. If you live somewhere with a very humid climate, it is possible that the outside air is too humid as well. In that case you can either buy a dehumidifier for the room in which the incubator is, or add some dehumidifying objects into the incubator itself. Both rice and paper towels work great for lowering the humidity in an incubator.

Little chick on hand

General tips and tricks

  • If your incubator has a too high level of humidity with the water reservoir filled, but too low when it is empty you might be able to replace the water reservoir with an ice block tray. In an ice block tray you can fill as many of the individual holders with water as is necessary for the perfect level of humidity.
  • If you don’t want to check on the humidity all the time, some incubators have fully automated humidity control systems available, such as the Brinsea Octagon 20 (Amazon link). If you want to read a review, read my Brinsea Octagon 20 review.
  • Don’t open the incubator during the actual hatching process in the last 1-2 days. This is because the humidity level may drop too far down, and humidity takes a lot longer than temperature to go up again.
  • Try out different levels of humidity during the incubation process. There are some subtle differences between different areas and different chicken breeds, so trial and error can help you find the perfect balance for your chickens.

Where to place your incubator

If you are still having trouble with the humidity in your incubator, consider placing the incubator elsewhere. Generally speaking the incubator is best placed inside your house, somewhere without large temperature fluctuations. So not next to the heating. In some climates it can actually be better to keep the incubator outside, especially if you have a good chicken coop. In nature everything happens outside as well of course. If you want to keep your incubator outside, or if you want to let your chickens hatch the eggs themselves, make sure you have a good chicken coop. A good chicken coop should be well isolated, and have plenty of space for brooding, hatching, and the chickens to stay in at night. Some examples of good chicken coops can be found in our best chicken coops article.

8 Responses to “How to control humidity in an incubator”

  1. I would love some advice. I have a smartxchoice incubator and I can’t get the humiduty level above 35-40%… I have the entire bottom filled with water as well as a small bowl of water with 2 rags coming out of each side and they are both soaked… I’m not sure what else to do I’m at a loss..can you offer any advice. Thank you in advance.

    • Danny says:

      Hello Tracey,

      That is quite surprising. I can’t be 100% sure over the internet, but I would assume that the incubator is broken, either the humidity measurement is incorrect, or the temperature isn’t high enough.

      You can test both by turning the incubator off, putting it inside a new room, letting it rest open and empty for a few hours, and then measuring the temperature and humidity inside the room before closing the incubator and seeing what it says. It should be pretty much the same, otherwise something is definitely broken.

      If that looks good, you can let the incubator run for a while while leaving a thermometer inside. Let the incubator do its job, then open it and see whether the inside thermometer agrees on the temperature.

      If your incubator turns out to actually work correctly, I would try putting the incubator elsewhere. Not outside, not anywhere with temperature swings such as close to anything that warms up, and definitely not in the bathroom as it gets very humid there.

      If that still doesn’t work, you might want to try and find someone local who also incubates chickens, as that person will be both familiar with your local weather, and can actually have a look at the incubator him/herself.

      Good luck!

  2. Laura says:

    What about humidity for duck eggs? Do the same rules apply with the percentage of air sack?

  3. Laura says:

    I’m really struggling to know how humid it is in there could you recommend a humidity gage that could go in with the eggs rolling around? It’s a very old but efficient incubator. The ice tray trick is a brilliant idea for when they’re on lock down as one of the trays under all the eggs is broken. I’m just blindly adding water to one tray once a week. So grateful for any advice.

    • Danny says:

      Hello Laura,

      There are plenty of small hygrometers available online, such as for example the ThermoPro TP50 Digital Hygrometer. Regular candling can do the work just fine as well. If the air sack is too small, lower humidity a bit, while it is too large, increase humidity a bit.

  4. Cheryl Fager says:

    Hello, This is my first time. I place my eggs in my incubator on Wednesday. Im having problems with keeping my humidity up. The manuel i recieved with my incubator said keep humidity between 50-65. I will have my humidity at 55% and in 2 hours its at 40%. Am I doing something wrong? I am afraid to be gone to long in case the humidity drops to low. Is that normal to drop like that and is it ok? Is there something I can do to help the humidity stay in the normal range? I have the incubator inside my house. Sorry for all the questions. Thank you, Cheryl

    • Danny says:

      Hello Cheryl,

      There can be plenty of reasons for the humidity to drop like that. It could be a faulty egg incubator or incorrect placement in your house.

      I don’t know what egg incubator you are currently using, but often they come with a water reservoir. Make sure it stays filled and the egg incubator should do its job. if that doesn’t work, putting a damp towel or sponge with the eggs may help.

      As for correct egg incubator placement, make sure there is no direct sunlight, no heating elements nearby, and no airflows either. Preferably keep your egg incubator in a room that is relatively stable in temperature and not too hot.

      If you’re doing everything right already then you’ll have to just wait and see. If the incubator ends up killing all the eggs, you may need to look for a new egg incubator. Brinsea egg incubators are by far the best, though also the most expensive. You can check a full list of the best egg incubators here.

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