FALL PROTECTION CALCULATIONS
Updated: Mar 28
Using a personal fall arrest system (PFAS) without evaluating fall clearance is like bungee jumping with a bungee cord that is too long. It places workers in a situation that can result in severe injury and death. Prior to using a PFAS employees must have a basic understanding of fall clearance. Calculating fall clearance takes the following factors into account:
The length of the connector including deceleration distance.
The length of the worker’s body.
An adequate safety factor.
Deceleration distance is the vertical distance a worker travels between the activation of the fall arrest system’s deceleration device and the final fall arrest (stop). A deceleration device, often referred to as an energy or shock absorber, is any mechanism that serves to dissipate energy during a fall. Deceleration distance cannot exceed 42 inches (3.5 feet).
Fall Clearance Calculator
Assume that a six-foot worker is wearing a body harness attached to a six-foot connector with a deceleration device. The connector is attached to the body harness’s dorsal D-ring and a suitable anchorage point. The following calculation provides the fall clearance distance requirement.
+ 3.5 feet of deceleration distance (energy/shock absorber)
= 9.5 feet of total fall distance
+ 6 foot – length of the worker’s body
= 15.5 feet
+ 3-foot safety factor
18.5 feet = fall clearance
Based on this example, the worker must ensure that the anchorage point is at least 18.5 feet above the lower level, obstruction, or dangerous machinery or equipment. If adequate clearance is not available, the worker should choose another suitable anchor point or consider using equipment such as an aerial lift, scaffold, or fall restraint system. A shorter connector may also decrease the required clearance distance.
Please take the time to make sure employees understand the importance of evaluating fall clearance. Failure to understand this basic concept is like bungee jumping with a bungee cord that is too long.
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Joe Mlynek is a partner and subject matter expert at Safety Made Simple, LLC. He has over 20 years of experience in safety at the corporate level and as a consultant. He is a Certified Safety Professional (CSP) and Occupational Safety and Health Technician (OHST). Joe can be reached at email@example.com