Negative pressure ventilation is the most popular ventilation system used by broiler producers in the Southeast. Through the use of exhaust fans and adjustable air inlets, growers have found that they can more easily rid the house of ammonia and excess moisture, maintain more consistent house temperatures, and at the same time keep energy usage to a minimum. These benefits are due to the fact that a negative pressure ventilation system gives the grower more control over air exchange and air dist...ribution. Controlling these two factors gives the grower more control over his paycheck. The amount of fresh air brought into the house can be accurately controlled through the use of exhaust fans and interval timers. If the grower wants 4,000 cfm of fresh air, he sets the timer on a couple of 36" fans for one minute out of five. If he wants twice as much fresh air, he doubles his timer setting. The grower doesn't have to concern himself with how hard the wind is blowing and from what direction. He knows that if his static pressure is right and his inlets are properly adjusted, the cold incoming air will mix with the warm air near the ceiling preventing bird chilling, thereby improving bird performance.