Ventilation in a poultry house supplies fresh air that is essential to sustain life. It also helps reduce the extremes of temperature, humidity and air contamination to tolerable limits for confined chickens. Improved ventilation systems have also made possible the high density populations of poultry in confinement, thus reducing the building cost per unit housed. This is economically important since it reduces production and labor costs. Ventilation air removes excess heat, moisture, dust and odors from the building and, at the same time, dilutes airborne disease organisms.