Vent-Axia 56 35 50 self programming electronic on/off wall mounted humidity sensor which reacts to any rapid increase in humidity and temperature by switching a Vent-Axia fan On for rapid removal of moisture laden air, in domestic bathrooms and kitchens. It can be wired into controller “Auto” mode connections. Night time RH increment setback feature suppresses nuisance tripping when the humidity level gradually rises as the temperature falls.