A retractable fall arrest device comprises a unit housing, a spring sub-assembly, a brake/clutch sub-assembly, and a drum assembly. The spring and brake/clutch sub-assemblies each include shaft portions which extend into the housing and are removably connected together or to the drum assembly, and support the drum assembly in the housing. The spring and brake/clutch assembly are themselves removably connected to the unit housing. Finally, the unit housing comprises two wall members (i.e., clam shells) which are removably connected together. This fall arrest device allows for replacement of any of the four constituent components of the device in the field, thus reducing the down time between repairs or recertification of a particular fall arrest device.