Rope Rescue Gear and Everything Between! Part 4 – Selecting a System Safety Factor

Written By: Lance Piatt

When it comes to ensuring safety, there are a number of factors that need to be taken into consideration. During training sessions, the safety standards could be lower than during rescue operations as trainees may not have the same level of experience and expertise. However, this does not mean that training sessions can be conducted without any regard for safety – instead, there should be an appropriate balance between safety and challenging the trainees. Furthermore, redundancy is also an important factor when considering safety – it is wise to have multiple backup plans in case of any unexpected events or hazards that occur during a training session or rescue operation. Ultimately, how much safety is enough will depend on the situation, but it is paramount that all safety protocols are strictly adhered to.

Currently there is set SSSF.  Highly trained mountain teams have been known to use a 4:1 SSSF.  Other teams have opted for 5:1, 7:1 or 10:1 SSSF.  Still others, such as legacy teams might still be attempting a 15:1 SSSF (which just about impossible and still get anything done).

Then there is something many teams still haven’t grasped yet… the “dynamic” end of things. A minimum of 2:1 DSSF factor has been suggested as a place to camp for a bit.  Because the relationship between dynamic and static SSFs is still being and tested, caution, data and knowledge is the best guide of all.

Common strengths 

  • 40 kN – NFPA General use carabiners
  • 36 kN – NFPA G pulleys, anchor plates
  • 22 kN – NFPA Technical use carabiners
  • 20 kN – NFPA Technical use rope
  • 22.2 kN –  (5,000 lbf) OSHA
  • 18 kN – NFPA Technical use pulleys

Rope Rescue Calculations

  • Mass – 2.2 lbs / 1 kg = 220 lbs (person) / 100 kg (person).
  • Acceleration makes the 220 lbs load = 1 kN load.
  • Two person load (rescuer and patient) is 2 kN load.


It is essential that you are knowledgeable in the concepts and can effectively use them with your equipment and systems. Knowing how to apply these concepts correctly will ensure that your equipment and systems function efficiently.

The rope rescue and rigging industry has come a long way in its development of equipment that meets the needs of those who rely on it. Manufacturers have implemented robust Quality Control programs to ensure that their products are up to the task, with performance requirements and testing standards having been greatly improved over the years. As such, rather than simply aiming to make their systems as strong as possible, manufacturers are now able to focus on whether or not a particular system is capable of performing the task at hand. This helps ensure that everyone involved in rope rescue and rigging operations can trust their equipment to perform reliably and safely when they need it most.

Static safety factor (SSF) is an important concept in rope rescue and rigging. Essentially, it is a measure of the strength of the system relative to the anticipated load. To calculate SSF, you must first identify the weakest link in the system – typically, this will be a component such as a carabiner or webbing loop – and then divide this by the anticipated load.  The higher the SSF, the stronger and safer the system.

Raising Systems

In rope rescue and rigging, the T-method is a useful tool for determining the highest load points in complex raising systems. It can help prevent dangerous scenarios from occurring when lifting heavy loads. For example, if a 3:1 haul system were used to lift an object or person, the component that would see the greatest dynamic load during the raise would be the haul rope grab. If the load were to become hung up while still being raised, a potentially worse case scenario could occur. By using the T-method, one can identify which point in the raising system sees the greatest load at any given time and make adjustments accordingly. This way, operators can ensure that their rescue or rigging operations are as safe as possible.

Lowering System

The original belay competency test was developed to ensure that individuals have the necessary skills and experience to safely and effectively perform rope rescue and rigging in a variety of environments. By simulating a worst case scenario during an edge transition, the test is designed to assess a person’s ability to use their knowledge and expertise in order to execute complex maneuvers while managing risk:

  • A rescue system set up relatively close to the edge with 3m of rope
  • A main line failure occurs during an edge transition resulting in a 1m drop on a non-tensioned belay line
  • The original performance criteria based on a 2kN load included a maximum system extension (stopping distance ) of 1m and a maximum peak impact force of 15kN.


The current NFPA criteria has established rigorous safety standards for rope rescue and rigging. In order to ensure that a rescue system is certified, the belay device must be designed in such a way that limits the peak impact force to 15kN. This is achieved by having a 60cm drop on a 3m of rope plus a maximum system extension of 1m of rope. It is important for the belay device to be designed with this criteria so that peak impact force does not exceed 15 kN.

Dynamic forces generated by a descending load in rigging and rope rescue operations can be substantially greater than typically expected static loads, due to the additional force that is exerted during its fall. This magnitude of force can reach its peak in a very short period of time, usually during the arrest phase. In order to ensure a successful outcome, it is crucial that proper preventive measures are taken to adequately manage these dynamic forces.

When rigging or performing a rope rescue, it is might be good to factor in load limiting equipment and make sure that all components used are rated and certified above the applicable weight limit. This is done to ensure safety of both the rescuer and the subject. Staying up-to-date on regulations and best practices for rope rescue is also important in order to guarantee a successful and safe outcome.

For those who are new to rope rescue, it’s important to take the time to study the process, understand the fundamentals of rigging, and always be conscious of your surroundings and the materials you are working with. Doing so will help ensure that any rope rescue you are involved with goes as safely and smoothly as possible.


Peace on your Days



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