The WETTY servo controlled respiratory gas humidifier combines modern technology and innovative design in a high performance unit. It has been designed for neonatal and pediatric use and it is characterized by high technology, ease of use and maintenance. The project design philosophy is characterized by its use of high technology components as well as its simplicity of use and easy mantainance. WETTY has a dual heating system. The first one consists in a humidifier chamber containing distilled water placed on a heating plate and heats and humidifiers the air that passes it through. The second one, placed along breathing circuit, heats the humidified gases avoiding humidity condensation. The control of air temperature is done by adjustment of the power supplied to the heating plate. The temperature is measured by temperature sensors in different points of the breathing circuit. Using the data measured, the software automatically calculates the power to be supplied to the plate obtaining the desired temperature. The humidity level can be set by the operator on 5 levels and displayed on a LED scale.