What Does
Fall Clearance Mean?
Fall clearance refers to the minimum distance required to safely arrest a person’s fall. Fall clearance is a critical calculation to ensure the safety of anyone working at height.
Accurate fall clearance calculations prevent fallen workers from coming into contact with obstructions below, reduces the risk of serious injury, and may prevent fatal accidents. It is also a critical factor in the selection of proper fall protection equipment.
Safeopedia Explains Fall Clearance
The fall arrest systems workers wear while working at height will only be useful if a certain distance is maintained between the worker and the surface below once the fall arrest system has been deployed. Accurate fall clearance calculations can, therefore, save lives.
Personal fall arrest systems includes several components:
- Anchorage
- Connectors
- Full-body harness
- Shock-absorbing lanyard
- Self-retracting lifeline
- Deceleration device
When considering these various components, it is important to ensure that they would arrest a fall safely. This includes assessing the fall clearance to ensure that there is sufficient distance for the fall arrest system to safely deploy without causing the worker to come into contact with any surface or obstructions, such as machinery and railings.
Calculating the Fall Clearance
The length of the lanyard and the height of the anchor point at which the worker ties off determine the freefall distance before the lanyard begins to slow the fall.
The calculation used is the following:
Fall Clearance = Length of the Lanyard + Deceleration Distance + Height of the Worker + Safety Factor
The Safety Factor in this case accounts for the various ways that the different components of the fall clearance system might shift, move out of place, elongate, or otherwise add further distance to the total fall clearance. It is typically about one meter.
The OSHA Training Toolbox Talk on Personal Fall Arrest Systems lists additional factors that determine the ultimate fall distance (or total fall distance):
- Deceleration distance: This is the maximum distance that a shock-absorbing lanyard will stretch to decelerate the fall. As per OSHA regulations, the deceleration distance should not be greater than three and a half feet.
- D-ring shift: This is the distance the D-ring moves and the harness shifts as it is jerked upward when the lanyard slows the freefall. The D-ring ends up higher on the worker’s back, and this distance is assumed to be one foot.
- Back D-ring height: This is the distance between the D-ring and shoe sole when the harness is worn. The default distance is 5 feet for workers who are 6 feet and shorter, and may have to be adjusted for taller workers.