Ventilation is often associated with respiratory health of animals; the quality of the air that animals breathe directly influences animal health and disease. Ventilation, directly and indirectly, impacts many other aspects of animal health as well. Good ventilation in the lying area of lactating animals helps bedding stay dry, a factor in favor of good mammary health. Good ventilation along alleys helps to keep walking surfaces dry, which contributes to healthy feet. Good ventilation may lead to greater productivity, eg, maintaining air movement in the eating area makes animals more comfortable, especially important during hot weather as an aid to maintaining dry matter intake. A comfortable, well-ventilated lying area encourages animals to lie down, an important contribution to many aspects of animal health.
During ventilation, outside air is brought into a barn where it collects moisture, heat, and other contaminants. Air is then exhausted to the outside. To determine ventilation rates, the focus is on the moisture content of the air, measured by relative humidity.