You can hatch fertile chicken eggs and other types of eggs at home in an incubator. You need an incubator to carefully control the conditions for the eggs. The temperature and humidity must be carefully monitored inside for the eggs to hatch. It is very easy to build one yourself out of inexpensive materials.
Building the Incubator
One kind of incubator is a convection type. In this type, air holes in the top and sides of the incubator enable airflow and even out the temperature and humidity inside. The airflow dries the air, however, so you will have to have a water tray to keep the air moist.
First, obtain a box to serve as housing for the incubator. It can be a cardboard box, an old cooler or a wooden crate. It does not matter what it is as long as it is clean and sturdy and has a cover. The cover may be hinged, but it is not necessary. You can line it with aluminium foil to help reflect the heat inside. Put a tray in the bottom to hold water that will provide humidity. A disposable aluminium pie tin makes a good water tray. Install a screen over this, held up by pieces of wood so that it clears the water tray.
Next, to provide heat, install four light sockets. Place one in each corner and install four incandescent bulbs up to 25 watts each. Put a thermometer inside, or you can buy a thermostat switch to connect to the lights. The switch will automatically turn the lights on and off to regulate the temperature, and you will not have to open the incubator to check the thermometer. Since even temperature is so critical to incubation, a thermostat switch is better than just a thermometer.
Drill half-inch ventilation holes in the four corners of the cover and two quarter-inch holes in each side just above where the eggs will lie. The ventilation holes will provide the airflow inside the incubator and help even out the temperature and humidity. The last piece of equipment needed is a hygrometer to monitor humidity. Place this so you can easily see it through one of the ventilation holes.
Another type of incubator is a still-air type in which there are no airholes. However, this type tends to have variations of temperature and humidity in layers within the box. If you do not place the thermometer and hygrometer in the proper place, readings will not tell you what conditions are like for the eggs. This causes eggs not to hatch. If you build this type, flush the air from the box completely four times a day to freshen it.
A third type is a forced-air incubator where a fan increases airflow within the unit. The incubator has ventilation holes, so maintaining proper humidity can become a problem.