A psychrometric chart is a graph of the thermodynamic parameters of (moist) air at a constant pressure; the chief parameters are wet and dry bulb temperature and absolute and relative humidity. The chart can therefore be used to map any site location (it may be adjusted for elevation relative to sea level) in order to map the specific, local needs of climate control in buildings. The yellow box encloses the area that humans consider to be 'comfortable', however this box can be expanded in various ways by applying certain types of climate control. E.g., rather than heating or cooling the air inside a building for it to be within the normally accepted temperature range, air temperature can stray beyond this range if a radiant heating or cooling source is provided.