A chicken egg incubator is used to automatically ensure the best conditions to allow the development of a chick that will eventually hatch from the egg.
All incubators use some form of heat source that is thermostatically controlled. This means that more or less heat energy will be emitted depending on how cold or warm it is outside. A thermostat can be set to a specific temperature and the automatic feedback means that the incubator will keep to this temperature.
Be sure to check the rating of the incubator before you buy. Although most incubators will work in most conditions, you may need a higher powered model if your room temperature is extremely low (e.g. in a garden shed in winter).
Better models will also feature a thermometer so that you can periodically check that everything is in good working order. Also, fan assistance is preferable as this ensures a better and more uniform distribution of heat.
chicken egg incubatorEggs need to be turned three to five times per day for best results. More expensive models feature automatic egg turning.
For best results you should control the humidity and not just the temperature. This is especially true if you live in a particularly humid or dry environment. This matters less for chicken eggs but more for eggs of more exotic birds such as birds of prey.
The best models feature an alarm system that will activate if the lid/door is not closed or sealed properly. Also, you can measure the ambient humidity using a device called a hygrometer.
Most consumer models allow you to incubate from as few as six to as many as sixty eggs in a single device. Commercial devices can incubate hundreds of eggs. The more eggs that you are incubating then the more strongly you should consider the feature of automatic egg turning.
If you are interested in incubating other eggs e.g. quail eggs, then most incubators allow you to interchange trays with slots of different sizes for this very purpose.