Fall Arrest System (PFAS) is an assembly of anchorage, full-body harness and connectors that stops a worker after a fall begins, within OSHA limits on arresting force, free fall and deceleration distance.
A personal fall arrest system (PFAS) is an assembly of an anchorage, a full-body harness and connecting equipment that stops a worker who has already fallen, before they hit a lower level, while limiting the force on their body. Unlike a guardrail or a restraint setup, a PFAS accepts that the fall happens and manages its outcome.
That distinction drives how the system is specified. A PFAS has to be strong enough to hold a dynamic load, give enough clearance below the worker to stop the fall in time, keep forces low enough to avoid internal injury, and come with a plan to get the worker down quickly. It sits low in the hierarchy of fall protection for that reason: useful and often necessary, but only after elimination and passive options have been ruled out.
Trainers often teach a PFAS as A, B, C, with D added for deceleration and rescue. Each piece has to be compatible with the others; mixing brands or bolting together parts never meant to work as a unit is a common audit finding.
The anchorage is the secure point the system ties back to: a beam clamp, a roof anchor, an engineered horizontal lifeline or a structural member. Both 29 CFR 1926.502(d)(15) and 1910.140(c)(13) require it to support at least 5,000 pounds per employee attached, or be designed, installed and used under the supervision of a qualified person as part of a complete system that keeps a safety factor of at least two. Conduit, handrails, ductwork and pipe hangers rarely meet either test.
Only a full-body harness is allowed for fall arrest. Body belts have been barred as part of a construction PFAS since January 1, 1998, and 1910.140(d)(3) prohibits them in general industry. A harness spreads arresting forces across the thighs, pelvis, chest and shoulders. Fit matters: loose leg straps can cause serious injury in an arrest.
Connectors include snap hooks, carabiners, lanyards and self-retracting lifelines (SRLs). Snap hooks and carabiners must be self-locking. Energy-absorbing lanyards tear open a packed web to slow the worker, and SRLs lock quickly, much like a seat belt, which usually cuts free fall and clearance needs.
OSHA does not just require that a fall be stopped. It sets limits on how the stop happens. Under 1926.502(d)(16) and 1910.140(d)(1), a PFAS used with a body harness must:
Any PFAS component that has arrested a fall must be removed from service until a competent person inspects it and confirms it is undamaged and safe to use again. In practice, most manufacturers tell users to retire a lanyard after a single arrest.
The ANSI/ASSP Z359 Fall Protection Code is the voluntary consensus family that most manufacturers design and test to. It goes further than OSHA in places, including SRL classes and program management under Z359.2. Specifying Z359-compliant equipment is common in contracts, and auditors frequently check labels against it.
Clearance is the vertical distance needed below the anchorage, or below the working surface, so that the worker stops before striking anything.
For a 6-foot energy-absorbing lanyard anchored at the dorsal D-ring height, a rough tally looks like this:
That totals roughly 17 to 18 feet below the anchor. On a mezzanine 12 feet high, the worker hits the floor. Swapping in an SRL, or moving the anchor overhead, usually solves it. Manufacturers publish clearance charts for their own devices, and those charts should be the reference, not a rule of thumb. Swing fall must also be considered when the anchor is not directly overhead.
Both 1926.502(d)(20) and 1910.140(c)(21) require employers to provide for prompt rescue of each employee after a fall. Calling emergency services is not a rescue plan on its own; responders may lack rope access equipment or be far away.
A worker hanging motionless in a harness can develop suspension trauma, also called orthostatic intolerance, as blood pools in the legs. Trauma straps, deployable foot loops, let a conscious worker stand and relieve pressure while waiting. Rescue options include pre-rigged rescue kits, aerial lifts staged nearby, or assisted-rescue SRLs. Practice the plan; a rescue kit nobody has opened is close to useless.
An oil and gas maintenance crew was replacing instrumentation on a pipe rack about 20 feet above grade at a gas processing plant. The permit listed harnesses and 6-foot shock-absorbing lanyards tied to the rack steel. During a pre-task review, the supervisor ran the clearance numbers and found that a worker standing on a lower platform, 11 feet above an access road, would have struck the road before the lanyard fully deployed.
The crew switched to overhead beam anchors with 30-foot SRLs on that level and kept lanyards only where the clearance was proven. The site also staged a rescue kit at the rack base and ran a 15-minute rescue drill before the job started. The drill showed the kit's haul line was too short for the highest work point, which the crew fixed before anyone climbed. The incident was logged as a near miss, and the clearance check was added to the plant's permit-to-work template.
Fall restraint keeps a worker from reaching the edge, so a fall never happens. The lanyard length and anchor position physically stop them short. Fall arrest lets the worker reach the edge and catches them after they go over. Restraint is generally preferred because there is no arrest force, no clearance problem and no rescue, but it only works when the work does not require reaching the edge itself.
OSHA requires inspection before each use for wear, damage and deterioration, and removal from service of anything defective. ANSI/ASSP Z359 adds periodic inspection by a competent person, typically at least annually, with frequency set by use and conditions. Many employers record these formal checks in an equipment inspection system so expired or failed harnesses are pulled automatically.
Only if the anchor is rated for both. The OSHA test is 5,000 pounds per employee attached, so a single-person anchor cannot take a second worker. An engineered anchor designed by a qualified person may be rated for multiple users with a safety factor of two. Check the anchor's label or the engineer's documentation; if neither exists, assume one person only.
There is no safe time that applies to everyone. Symptoms of suspension intolerance can appear within minutes for some people, especially if they are injured, unconscious or dehydrated. That is why the rule is prompt rescue, not a fixed number. Plan rescue to start right away and design it so the worker is reached and relieved well inside a few minutes.
Part of SafetyIQ's EHS glossary: plain-English definitions of workplace health and safety terms.
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