A fall arrest system is a set of connected equipment designed to stop a worker mid-fall and limit the forces on their body so they survive without serious injury. It’s required on any construction site where workers are exposed to a fall of 6 feet or more, and in general industry at 4 feet. The system has three core components, often called the ABCs: an anchorage point, a body harness, and a connector that links the two together.
The Three Core Components
Every personal fall arrest system relies on the same basic chain: something solid to attach to, something worn on the body, and something connecting those two things. If any one link fails, the whole system fails. Here’s how each piece works.
Anchorage
The anchorage is the fixed attachment point, typically a steel beam, a roof anchor, or an engineered tie-off point. It needs to support at least 5,000 pounds of force per worker attached to it. That number isn’t arbitrary: OSHA requires it because a falling body generates enormous peak forces, and the anchor must handle that load with a wide safety margin. As an alternative, the anchor can be part of a system designed by a qualified person that maintains a safety factor of at least two, meaning the anchor can handle twice the maximum force the system would actually produce in a fall.
Anchorages must also be independent of anything supporting a work platform. You can’t tie off to the same beam holding up your scaffold, because a single failure would take both the platform and your fall protection with it.
Body Harness
The harness is what the worker wears. Unlike an old-style body belt, a full-body harness distributes the shock of a fall across the thighs, pelvis, waist, chest, and shoulders. This spread of force is critical. Concentrating all the stopping force on your waist (as a belt does) can cause serious internal injuries. The harness includes one or more D-rings, which are the attachment points where connectors clip in. Most harnesses have a dorsal D-ring between the shoulder blades for fall arrest, and some include additional rings at the chest or hips for positioning or retrieval.
Connectors
Connectors are the links between the harness and the anchor. The most common type is a lanyard: a flexible strap with a clip at each end, one for the harness D-ring and one for the anchorage point. Connectors also include carabiners, snap hooks, and self-retracting lifelines (devices that unspool like a seatbelt and lock instantly when they detect a sudden pull). Many lanyards include a built-in shock absorber, a woven pack that tears open in a controlled way during a fall to reduce the peak force on your body.
How the System Stops a Fall
When a worker falls, the lanyard or self-retracting lifeline goes taut and begins transferring force to the anchorage. If a shock-absorbing lanyard is in the system, its energy absorber deploys, extending and slowing the stop over a longer distance. This reduces the peak force that reaches the worker’s body. The full-body harness then distributes that reduced force across multiple points instead of concentrating it in one area.
The total distance a worker drops before coming to a complete stop is called the fall distance, and it matters for planning. You need to account for the length of the lanyard, the stretch of the shock absorber (which can add 3.5 feet), harness stretch, and the worker’s height. If there isn’t enough clearance below the work surface to accommodate that total distance, the worker hits the ground before the system finishes doing its job. This is why fall distance calculations are done before work begins, not after a fall.
OSHA Requirements
Federal regulations under OSHA’s construction standards (29 CFR 1926.502) and general industry standards (29 CFR 1910.140) lay out the rules. The anchor must hold 5,000 pounds per attached worker, or be engineered with a safety factor of at least two. Employers must also provide for prompt rescue after a fall. That last point is easy to overlook, but it’s a legal requirement and a medical necessity.
The regulations don’t define “prompt rescue” with a specific number of minutes, which puts the burden on employers to have a realistic plan in place. Calling 911 and waiting is not generally considered an adequate rescue plan, because the medical risks of hanging in a harness begin quickly.
Why Rescue Time Matters
A worker who is caught by a fall arrest system is alive, but they’re now hanging in a harness, and that creates its own danger. Suspension syndrome (also called suspension trauma) happens when the harness straps compress the blood vessels in the legs, causing blood to pool in the lower body instead of returning to the heart and brain.
Symptoms can begin within minutes and include dizziness, confusion, nausea, cold sweats, blurred vision, pale skin, and a slowing heart rate. Without rescue, the worker can lose consciousness. In rare cases, the heart can stop entirely. There is no reliable fixed timeline for how quickly this progresses, which is why having a rescue plan with the right equipment and trained personnel on site is not optional. Workers should also know to pump their legs and avoid going limp if they’re conscious and suspended, since muscle movement helps push blood back up toward the heart.
Inspecting Your Equipment
Fall arrest equipment needs to be inspected before every use. A harness that looks fine at a glance can have damage that compromises its strength. OSHA’s inspection guidelines list specific fail criteria that require removing a harness from service immediately:
- Webbing damage: cuts, tears, fraying, broken fibers, or undue stretching (which can indicate the harness has already arrested a fall)
- Heat or UV damage: hard or shiny spots on webbing, burnt or charred fibers, or excessive brittleness
- Chemical exposure: discoloration from chemical contact, mildew, or overall deterioration
- Stitching problems: pulled, cut, or missing stitches
- Hardware issues: twisted or bent metal, rough or sharp edges, rust, corrosion, cracked buckles, or distorted grommets
- User modifications: any changes made by the worker, such as drilling additional holes or altering straps
- Missing or illegible tags: if you can’t read the manufacturer’s label or the inspection tag, the harness comes out of service
Any harness that has actually arrested a fall should be removed from service and not reused, even if it looks undamaged. The forces involved can cause internal damage to webbing and stitching that isn’t visible. The same applies to lanyards and shock absorbers.
Storage matters too. Harnesses should never be stored near batteries or chemicals, since a leaking battery can cause acid damage to the webbing. Keep them in a dry, cool area out of direct sunlight, and check the manufacturer’s recommended service life. Most manufacturers set a lifespan of around five years from the date of first use, though this varies.
Fall Arrest vs. Fall Prevention vs. Fall Restraint
These terms sound similar but describe different approaches. A fall prevention system, like a guardrail, stops the fall from happening at all by creating a physical barrier. A fall restraint system uses a short lanyard or tie-off that physically prevents you from reaching the edge where a fall could occur. You can’t fall because the system won’t let you get close enough.
A fall arrest system, by contrast, allows the fall to happen but catches you during it. It’s the last line of defense when guardrails and restraint systems aren’t feasible. Because the worker actually falls before the system engages, fall arrest introduces higher forces on the body and requires the most careful planning around clearance distances, anchor strength, and rescue.