Series PAS Pneumatic Sensing Switches are general purpose proving switches for HVAC and Energy Management applications where pneumatic actuation is required (such as intrinsically safe environ¬ments or any area where it is desirable to avoid electrical arcing).. They sense the flow of air and provide a proportional pneumatic signal for alarm or control. PAS switches can sense static or differential air pressure up to 2.0″ w.c. (PAS-2100 models) or 12.0″ w.c. (PAS-2200 models). The pneumatic switch vents a restricted compressed air source until reaching set point; switch actuation occurs at set point, closing the vent and sending a full pressure pneumatic signal to an electri¬cal switch outside of the hazardous area, or actuating a pneumatically driven element directly.