Most light controlled pullet houses in the United States do not have enough inlet and fan light trap area. As a result, it is not uncommon to find pullet house exhaust fans operating at less than 60% of their rated capacity. The reason that little has been done to address this problem is that pullets are on restricted feed and are placed at very low densities mortality problems are extremely rare, and the loss in ventilation fan efficiency is not easily recognized as a real problem. Complicating... matters is the fact that until recently there was little or no reliable information on the proper amount of light trap to install. In addition, light traps are fairly expensive and the amount of light trap area installed was often minimized in an effort to cut costs.