The air pressure switch is a safety device which checks the fan is fully operational. It ensures that, if the fan fails within the boiler, there would not be a build up of dangerous gasses with no means of removing them safely. The printed circuit board

Brand Name	Myson
Colour	None
Material	None
Manufacturer Model No	402A3410
Wear Type	None
Type	Air Pressure Switch
Certifications Met	None
Country of Origin	None
Protects From	None
Waterproof	None
Number of Pockets	None
Waist Size	ab32cg57gw
Toilet Cistern Capacity	FTW
ERP Rating	Not Applicable
Supplier Part Number	402A3410