How is air taken into the bottle when the contents are discharged from the pump?
When the contents are discharged from the pump, there is an airway which opens to take in air into the bottle. When pumping, space between the screw cap and the piston through the side orifice of the cylinder, different from the channel for discharging the contents, leads air into the bottle. This airway is closed to avoid any leakage when not pumping.
