A Fall Arrest System (FAS) is a safety method designed to halt a worker’s descent after a fall has occurred, preventing impact with the ground or a lower level. This system functions as the final layer of defense where eliminating the fall hazard is impossible. It is engineered to absorb and dissipate the energy generated during a fall, suspending the worker safely until a rescue can be executed. Understanding the mechanics and required setup of this system is foundational to safety in elevated work areas.
Distinguishing Between Fall Protection Methods
A Personal Fall Arrest System (PFAS) operates reactively, engaging only after the worker has lost control and begun to fall. This contrasts sharply with proactive methods like Fall Restraint Systems. Fall Restraint utilizes equipment, such as a fixed-length lanyard, to physically prevent the worker from reaching the edge of a walking surface where a fall hazard exists.
Work Positioning is designed to support a worker at a height, allowing them to use both hands freely while performing a task. Work positioning is not intended to provide complete fall protection and must be used in conjunction with a separate fall arrest system. The fundamental difference is that restraint is a preventative measure, while arrest is an intervention measure stopping the worker after exposure to the hazard.
The Three Essential Components of a PFAS
The functionality of a Personal Fall Arrest System relies on three interconnected elements, often referred to as the “ABC” of fall protection.
Anchorage (A)
Anchorage is the secure point of attachment for the system. Anchorage points must support an imposed load of at least 5,000 pounds per worker attached, or be engineered to maintain a safety factor of at least two times the maximum anticipated arresting force.
Body Support (B)
Body Support is provided by a full-body harness that distributes impact forces across the stronger parts of the body, including the thighs, pelvis, chest, and shoulders. Proper fit is important, ensuring the harness webbing is snug and the dorsal D-ring, the typical attachment point, is correctly positioned between the shoulder blades. This placement helps maintain an upright posture during a fall and subsequent suspension.
Connecting Device (C)
The Connecting Device links the body support to the anchorage point. This device may be a shock-absorbing lanyard or a synthetic web or rope line containing an internal mechanism to slow the descent. Self-Retracting Lifelines (SRLs), which automatically take up slack and lock quickly when acceleration is detected, are also used. Many connecting devices incorporate an energy absorber, often called a shock pack, which deploys to limit the force transmitted to the worker’s body upon arrest.
Understanding Clearance and Fall Dynamics
Safe deployment of a Fall Arrest System depends on calculating the Total Required Clearance. This is the minimum vertical distance needed between the worker’s feet and the lower level to ensure the fallen worker does not strike the surface below upon complete arrest.
The calculation involves several components:
- Free Fall Distance: The length the worker falls before the system engages, legally limited to a maximum of six feet.
- Deceleration Distance: The length the shock-absorbing mechanism extends or deploys to slow the fall. A typical shock absorber can extend up to three and a half feet while dissipating energy.
- Harness Stretch and D-ring Movement: Accounts for the minor shifting of the harness and connection point under the worker’s weight.
- Safety Factor: Typically mandated as three feet, this buffer is added against miscalculation or unforeseen variables.
If the working height is less than the calculated Total Required Clearance, a PFAS cannot be safely used. Workers must also account for the hazard of a swing fall, which occurs when the anchorage point is not directly overhead and the arrested worker swings like a pendulum, potentially striking an adjacent structure.
Key Regulatory Requirements and Standards
The use and performance specifications for Fall Arrest Systems are legally governed in the United States by the Occupational Safety and Health Administration (OSHA). Requirements for the construction industry are detailed under 29 CFR 1926.502, while general industry operations are covered by 29 CFR 1910.140. These regulations set performance parameters for all system components.
A primary requirement is the limitation of the Maximum Arresting Force (MAF) exerted on the worker’s body during the fall. OSHA mandates that the MAF cannot exceed 1,800 pounds of force when a non-shock-absorbing lanyard is used. When a system incorporates an energy-absorbing device, the MAF must be limited to a maximum of 900 pounds. Manufacturers often adhere to guidelines established by the American National Standards Institute (ANSI) to ensure product quality beyond minimum regulatory mandates.
Ensuring System Reliability Through Inspection and Training
Maintaining the integrity of a Fall Arrest System requires inspection and training. Every worker is responsible for conducting a pre-use inspection of their harness, lanyard, and connecting devices before each shift, checking for cuts, frayed webbing, or damage.
More comprehensive, scheduled inspections must be performed by a designated competent person at regular intervals, often monthly. Additionally, a qualified person, such as a manufacturer’s representative, must conduct an annual inspection to verify the equipment’s continued fitness for service.
Training is mandatory for all users, covering proper techniques for donning the harness, performing inspections, and understanding the site-specific rescue plan. Any component of a PFAS subjected to the forces of an arrested fall must be immediately removed from service and destroyed, as its structural integrity can no longer be guaranteed.