This post was written by Rigid Lifelines, a provider of fall protection and fall arrest systems. They provide fall safety solutions to a variety of different industries.

The terminology surrounding fall protection systems may seem complex, but it is important to understand the basic systems and terms to choose the fall protection solution best suited to a customer’s needs.  For example, the terms “fall arrest” and “fall restraint” may at first glance seem indistinguishable. Both fall under the rubric of “fall protection,” but there are important distinctions.

The main difference between arrest and restraint is an “arrest” occurs after a person freefalls through space. In other words, the system stops a worker’s fall that has already occurred, preventing impact at a lower level. In a fall restraint system, however, the worker is restrained from reaching a fall hazard. In such cases, the fall restraint would typically be provided by a fixed-length lanyard and a body harness or body belt. The lanyard acts as a leash, preventing the worker from reaching the leading edge.

Fall arrest systems are required when a worker is able to reach the leading edge and their center of gravity can breach it. In the event of a fall from an elevated position, the worker’s potential energy is converted to kinetic energy. Upon termination of the fall, the worker will impact a lower level unless he or she is decelerated in some manner. Unfortunately, absorption of kinetic energy presents the greatest challenge to the design and implementation of an effective fall arrest system. The basic idea is to engineer a system that prevents the worker’s body from absorbing all of the kinetic energy (as would occur upon impact to a lower level) and instead have a fall arrest system absorb the energy. Typical energy absorbers used in fall arrest systems include shock packs, rip stitch lanyards, or disk break mechanisms. Regardless of the method chosen, the energy absorber functions to decelerate the falling worker to zero miles per hour, thus preventing any injury that would have occurred had he or she reached a lower level or obstacle.

In regard to the technical differences between fall arrest and fall restraint, the expanded definition of fall restraint is a working surface from zero degrees up to 18.4 degrees of slope. The 18.4 degree slope* is used because it is a common 3/12 pitch on a roof. At slope angles greater than 18.4 degrees, the work environment demands a fall arrest system because a worker can no longer be restrained from an edge. The slope itself becomes the fall hazard.

By understanding workers’ environments and the nature of the fall hazards they face, the process of choosing the right fall protection system should become straight forward.

*the “18.4 degrees of slope” comes from ANSI Standard Z359.3 – Subsection 3.2.2. This standard was released in 2007. ANSI standards are not the governing law like OSHA, but ANSI standards are recognized internationally and can be referenced by OSHA under the general duty clause. ANSI standards can be adopted by any country. They have been adopted by the United States, Saudi Arabia, and many others.