Larry Kerr, age 11, of Tacoma, Wash., for his question:

HOW DOES AN EGG INCUBATOR WORK?

           Most commercial chicken incubators are electrically heated to    

maintain a constant temperature of from 99.5 degrees Fahrenheit to 100 degrees Fahrenheit. A system of fans circulate warm air through the egg chamber and over the fertilized eggs.

Can you believe this: large egg incubators today can hold up to 100,000 eggs. This is really truel

Incubation keeps the relative humidity at about 60 percent to reduce the loss of water content from the eggs. Mechanical devices turn the eggs several times daily, turning all the eggs at the same time.

Fresh air brought into the incubator keeps the oxygen level at 21 percent, the normal level of outside air.

Chicken eggs normally incubate for about 21 days.