When we consider cooling birds, most producers first turn to a fan for help. Fans do a great job of reducing temperature of a poultry house by using convection to help remove heat that is surrounding the bird. Birds use the evaporation of water from their respiratory system to help cool their bodies. Larger comb varieties also cool themselves by circulating blood through their comb and wattles. Testing the air by using a hygrometer to test temperature depression using ventilation is a simple method to determine the possible effectiveness of using fans.
Two things a caretaker should concern themselves during hot weather. Keeping the fans running efficiently, and running them long enough to help the birds cool properly.
Proper fan maintenance, includes brushing off shutters and doors to keep them free of any dirt and debris. This also includes the brushing off of fan blades so that they will "Bite" the air properly to move air through the fan. Do not attempt to brush off a fan without stopping electrical power to the unit. Do not forget to brush off the motor, as even sealed motors can cool better when not covered in dust! While brushing off fans, check belts and pulleys for wear and replace these as soon as possible. Worn pulleys will actually slow down a fan reducing the volume of air that can be moved.
Lastly, fans should run long enough to bring house temps down long enough for the birds to rest from heat stress. Consider overshooting house temp by allowing a house to cool to 70 degrees long enough for birds to eat and digest their food. If done during the cool part of the day, egg production and growth in meat birds should continue even on the weeks of high daily temperatures.