A dry fire protection sprinkler in which, when a ratio of a pressure P1 of a pressurized fluid in a flexible tube to a pressure P3 of the fluid in a fluid supply line is less than a predetermined ratio of at least 3 to 1, a differential pressure controller sends a signal to a control valve to open, in order to allow the pressurized fluid in a pressurized fluid source at a pressure of P2 to enter the flexible tube, and, when the ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line equals the predetermined ratio, the differential pressure controller sends a signal to the control valve to close.