The Saunier Duval air pressure switch is a safety mechanism that ensures the fan is in full working order. It ensures that, if the fan fails within the boiler, there will not be a build up of noxious gases with no means of venting them. The printed circuit board closely monitors the air pressure switch to make sure it is completely functional before the unit is fired up, preventing the appliance from starting without one of its key safety mechanisms.

Brand Name	Saunier Duval