The Ariston air pressure switch is a spare part for euroCombi, Genus, microCombi, microSystem, Dia, Challenger, Excalibur and microGenus boilers. An air pressure switch is a critical safety device that ensures the boiler fan is working properly and prevents the accumulation of toxic gases in the event of a fan failure. The printed circuit board of the unit closely monitors the air pressure switch to ensure it is fully functional before powering on the system. This prevents the appliance from starting without the presence and operation of key safety features.