One barrier to adoption of natural ventilation is the knowledge that application in inappropriate climates or during inappropriate hours could lead to conditions in buildings which may affect both comfort and IAQ. As such, designers must diligently determine whether a climate is appropriate for natural ventilation. A series of tests on the typical meteorological year weather data can be used for this purpose. For many US climates, even mild climates, under normal design conditions, natural ventilation alone may not assure occupant satisfaction. In most cases, spaces may be advised to use mixed-mode ventilation systems, which combine natural ventilation and mechanical ventilation.