Knowing how much to ventilate during cold weather is crucial to a producer’s bottom line. Ventilating too little can lead to poor air/litter quality, resulting in bird health and performance issues. Ventilating too much can lead to drafty conditions and high heating costs. The first step to knowing how much you need to ventilate during cold weather is to understand which air quality variables are most likely to cause problems. In short, the three primary air quality variables poultry producers... need to manage, besides temperature, in a poultry house during cold weather are carbon dioxide, humidity, and ammonia. To maximize bird performance we would ideally like to keep carbon dioxide concentrations below 5,000 ppm, relative humidity around 60%, and ammonia concentrations below 30 ppm.