The Humid air is the name given to the Air by the scientists using the air like vector of Steam such as the climatologists, heat engineers and engineers of the Génie of the processes.

The humid air will be characterized by several sizes which one will keep traditionally:

• the Temperature (known as temperature dries)
• the wet temperature or wet Température of thermometer
• the temperature of dew or Dewpoint
• the absolute Humidité or water content
• the relative Humidité
• the Enthalpie

All these sizes are not independent. To know two sizes makes it possible to calculate all the others. Thus, these various parameters were gathered in diagrams called diagrams enthalpic of the humid air different according to the variables independent chosen and on which figures 4 types of curves (Enthalpy, Température, Water content and relative Humidité):

• diagrams of Carrier (water content according to the temperature)

• diagrams of Mollier (enthalpy according to the water content according to the temperature in Cartesian coordinates)
• diagrams of Mollier-Ramzin (enthalpy according to the water content according to the temperature in oblique coordinates)
• diagrams of Mahn (enthalpy according to the relative humidity)
• diagrams of Höhn (enthalpy according to the temperature)