A personal fall arrest system is the last line of defense. Remove the fall hazard first. Where it cannot be removed, keep the worker away from it, with guarding or with travel restraint that stops them reaching a position from which they could fall. Personal fall arrest is what is left when none of that is possible, and when it is the answer, it has to be complete. The familiar mnemonic covers three parts: Anchorage, Body support, and Connecting devices. Some versions add a D for descent and rescue. In this guide Fall Labs uses D for Drop prevention, because tools and equipment falling from height are a separate hazard to the people below and the original three letters do not cover them. Rescue is not dropped. It remains an essential part of planning whenever personal fall arrest is used, and it has its own place on this page.
Rescue is a requirement, not an option. The Occupational Safety and Health Administration (OSHA) requires the employer to provide for prompt rescue after a fall. In general industry the rule is in Title 29 of the Code of Federal Regulations (CFR), at 29 CFR 1910.140(c)(21). In construction, 29 CFR 1926.502(d)(20) allows the alternative of assuring that employees are able to rescue themselves. Do not assume a worker will be able to self-rescue, and do not assume emergency services can perform the rescue unless that has been verified and arranged. Write the plan down before work starts.
Four letters, two hazards
A, B and C are links in one chain, running from the anchorage to the worker. D covers the tools and equipment carried up with them.
- A Anchorage The secure point of attachment to the structure. 5,000 lb per attached worker, or designed, installed and used under a qualified person’s supervision as part of a complete system with a safety factor of at least two.
- B Body support The full body harness that holds the worker and spreads the arresting force across the body rather than concentrating it.
- C Connecting devices The lanyard or self-retracting device that links harness to anchorage, including whatever manages the energy of a fall and the snaphooks or carabiners at each end.
- D Drop prevention Tethers, attachment points and containers that keep tools and equipment secured at height, so a dropped object does not become the next incident.
A: Anchorage
The anchorage is the point that holds everything. OSHA requires it to support 5,000 lb for each worker attached, or to be designed, installed and used under the supervision of a qualified person as part of a complete system that maintains a safety factor of at least two (1910.140(c)(13); 1926.502(d)(15)). It also has to be independent of any anchorage used to suspend workers or to support or suspend a platform (1910.140(c)(12); 1926.502(d)(15)), so one failure does not take out both. The strength on a label is only half the story, because the label rates the anchorage connector, not the structure or substrate (the material the anchorage connector fixes into, such as concrete, steel or timber) it is attached to. An anchorage connector rated to 5,000 lb, attached to a supporting member or substrate that cannot carry that load, does not give you a 5,000 lb anchorage. Fall Labs recommends tying off as high as possible, with an overhead anchorage preferred unless a competent person determines it would create other hazards. Descent and rescue equipment requires anchorages suitable for the planned system and loads.
B: Body support
Body support means a full body harness, and only a full body harness. Body belts are prohibited as part of a personal fall arrest system (1910.140(d)(3)), and in construction they have not been acceptable since January 1, 1998 (1926.502(d)). The reason is biomechanical: a harness distributes the force of an arrest across the thighs, pelvis, waist, chest, and shoulders, while a belt concentrates it at the waist. For fall arrest, OSHA locates the harness attachment point in the center of the back near shoulder level, the dorsal D-ring. General industry permits the pre-sternal position only if free fall is limited to 2 ft or less (1910.140(c)(22)). The construction rule also permits an attachment point above the wearer’s head (1926.502(d)(17)). What the harness must withstand as a product is set by ANSI/ASSP Z359.11-2021, the full body harness standard published by the American Society of Safety Professionals (ASSP) and approved through the American National Standards Institute (ANSI).
C: Connecting devices
Connecting devices are the lanyards, self-retracting devices, and the connectors between them. Rescue and descent equipment has its own standard, ANSI/ASSP Z359.4-2013 (R2022), and equipment that meets it is not, by that fact alone, suitable for fall arrest.
Together, the connecting devices form the subsystem between harness and anchorage, and it is where most of the engineering hides. The lanyard or self-retracting device carries the load, and its energy management is what keeps the complete system within the OSHA limit on maximum arresting force, 1,800 lb with a harness (1910.140(d)(1)(i); 1926.502(d)(16)(ii)). A lanyard does that with an energy absorber. A self-retracting device can use one of several mechanisms, such as a brake inside the housing or an energy absorber in the line, so follow the device’s own instructions. The hardware at each end has to hold too: D-rings and snaphooks need a minimum tensile strength of 5,000 lb and a 3,600 lb proof test, and snaphooks have to be the locking type (1910.140(c)(7) to (9); 1926.502(d)(3) to (5)).
Roll-out. Unless the hardware is designed for the connection, a snaphook or carabiner must not be connected directly to webbing, rope, or wire rope; to another snaphook or carabiner; to a D-ring that already has another connector attached; to a horizontal lifeline; or to any object so incompatibly shaped or dimensioned that it could depress the gate and release itself (1910.140(c)(10); 1926.502(d)(6)). A connection like that can “roll out” under load and release. See the Z359 guide for the standard that governs connecting components.
D: Drop prevention
Drop prevention is not about protecting the worker from a fall, but about keeping tools and equipment from falling on the people below. ANSI/ISEA 121-2023, the dropped object prevention standard developed under the International Safety Equipment Association (ISEA), sets design, performance, testing, and labeling requirements for four categories of equipment: anchor attachments, tool attachments, tool tethers, and containers. It has its own plain-language walkthrough in ANSI/ISEA 121 explained.
Two hazards, one plan
A, B and C protect the worker in a fall. D protects everyone below from what the worker carries up. Address both, and plan for rescue before work begins.
