Calculating the correct fall clearance when using personal fall arrest systems may help prevent serious or fatal workplace injuries. Particularly when the accidents occur from heights, workers may suffer serious injuries or death due to falling. Falls rank as the leading cause of work-related deaths for construction workers, causing 33.5% of all occupational fatalities in 2018.

Using Personal Fall Arrest Systems

Personal fall arrest systems, or PFASs, typically include an anchorage and connectors, a retractable lifeline, a shock-absorbing lanyard, a full-body harness, and in some cases, a deceleration system that works together to help catch workers in the event of a fall. Should workers fail to correctly calculate their fall clearance before using PFASs, however, these systems may prove ineffective and catastrophic accidents may still occur.

The Length of the Lanyard, Deceleration Device, and Harness

Calculating fall clearance requires workers to account for the length of the lanyard and to consider the additional length added by a deceleration device and stretching of the harness. Deceleration devices may add up to three and a half feet to the lanyard’s length and stretching of the harness due to a fall may add another foot to the necessary clearance.

The Length of the Anchorage Point Connector

The forces placed on lifelines during a fall may cause sag, which adds the needed fall clearance. High tension lines may add up to 3% to the total length of the PFAS, while lines with shock absorbers may add up to 15% to the system’s total length. Taking this into consideration when calculating their fall clearance may help workers achieve effective fall protection.

The Length of the User’s Body

When using a PFAS, workers must account for the length of their bodies. A PFAS that stops a user at 16-feet may seem adequate for a project with a 14-foot elevation, but if the worker’s height exceeds two-feet, this may still allow them to strike a surface. Therefore, workers may include approximately five extra feet to their distances when calculating their fall clearances.

Allowing a Safety Buffer

To calculate their fall clearances when using PFASs, construction workers should include the lengths for the lanyard and harness, the anchorage point’s sag, and their bodies. Additionally, they may add on a safety factor of an additional three feet. Should their project’s height not allow the necessary clearance for the safe use of a PFAS, workers may consider alternative options.