Abstract: A device for safely lowering persons from upright structures such as buildings during an emergency at a safe, predetermined speed of no more than about four feet per second irrespective of the weight of the person being lowered. The device has a drum about which a cable is wound, a gear pump driven by the drum via a reduction gear train, and a hydraulic circuit which includes the gear pump and a flow control valve which maintains a constant hydraulic fluid flow through the circuit irrespective of the weight of the person being lowered and, therefore, also irrespective of the fluid pressure generated by the pump during operation. The hydraulic circuit is in fluid communication with a hydraulic fluid tank having an exterior surface dimensioned to cool the hydraulic fluid and prevent its temperature from rising by more than about 200.degree. F. above the ambient temperature during operation of the device.