Excessive air leakage from the bottom of tunnel curtains can be an expensive problem for poultry producers to deal with both in terms of fuel usage and bird performance. In many tunnel-ventilated houses the amount of cold air entering around loose fitting tunnel curtains is nearly equal to that entering through side wall inlets when minimum ventilating during cold weather. This surplus of cold air can cause the brooders/furnaces in the vicinity of the tunnel curtain to operate as much as three t...imes more as those in other areas in the house. Furthermore, the cold air entering from around the base of the tunnel curtain quickly drops to the floor chilling the chicks and leading to litter caking. Caked litter of course results in increased ammonia production, breast blisters and water height adjustment problems. While birds in the vicinity of tunnel curtain have problems because they are receiving too much fresh air, those in other areas of the house may suffer from poor air quality because they are not receiving their fair share of the fresh air brought in by timer fans.