Method and device for air conditioning in vehicles

An air conditioning system for a passenger cabin of a vehicle or an aircraft, comprising:

• means for continuously withdrawing air from said passenger cabin;
• limiting means for limiting a portion of the air withdrawn from said passenger cabin to be returned to said passenger cabin;
• means for discharging a remainder of the air withdrawn from said passenger cabin to the outside of said vehicle or aircraft;
• means for continuously mixing the limited portion of the air withdrawn from said passenger cabin with outside air to form replacement air containing a proportion of air withdrawn from said passenger cabin;
• means for heating said outside air to be mixed with said limited portion of air to a temperature just below that of air in said passenger cabin;
• means for continuously supplying said passenger cabin with said replacement air;
• at least one CO2 sensor for detecting a content of CO2 of air in said passenger cabin and producing an output signal;
• a humidity sensor for detecting humidity of air in said passenger cabin and producing an output signal;
• and
• a controller for receiving said output signal of said at least one CO2 sensor and said humidity sensor and controlling said limiting means so that said content of CO2 does not exceed a threshold value, and adjusting the humidity of said replacement air so that a relative humidity of the air in said passenger cabin is maintained in a range of values which are greater than a relative humidity of said outside air would be at said temperature of the air in said passenger cabin,
• wherein said controller adjusts the humidity of said replacement air by further controlling the proportion of air withdrawn from said passenger cabin in said replacement air, whilst maintaining the content of CO2 in the air in said passenger cabin below said threshold value.