One of the phenomena that affect the water loss in newborn infants is the humidity. The evaporation is determined by the vapour partial pressure. As well as temperature control, the reduction of the vapour partial pressure oscillations has an important role in the establishment of thermal comfort for newborn infants in incubators. This work presents an algorithm based on multiple models to water vapour partial pressure control. The tests have been made in an acrylic prototype simulating a commercial incubator. The results shows that the implemented control algorithm presents oscillations minor to +/-0.08 kPa.