The Schneider Electric (Barber Colman) M-225 Squeeze Bulb Tool-85 is a handheld accessory designed for testing and calibrating pneumatic HVAC control systems. It operates by manually generating air pressure through a squeeze bulb, allowing technicians to simulate control signals and verify actuator or controller response. Commonly used with pneumatic thermostats, dampers, and valve actuators, it supports accurate system diagnostics and adjustment.