Commercial incubation is accomplished at approximately 99.5 degrees F. Temperature can be controlled within plus or minus 0.1 degrees F.Small incubators cannot be controlled that closely. If control is within plus or minus 2 degrees F, hatching is usually successful. Sources for incubators. The amount of moisture that is in the air is the relative humidity. It is usually measured by a wet bulb thermometer.
Function depends on the cooling caused by evaporating water.
A thermometer is covered by a cloth sleeve that extends into a container of water. Humidity must be regulated. 91 degrees F for the last 3 days. Humidity should be set so that an egg loses 13 percent of its initial weight by the last 2 days before hatching. Too much or too little humidity in the incubator will cause hatching problems and the death of embryos.