Which of the following tasks requires the use of a personal fall protection system?

The task that involves working from a scissor lift when elevated above four feet necessitates the use of a personal fall protection system due to the increased risk of falls from heights. When personnel are working at elevated levels, particularly in environments with the potential for sudden movement or instability, the implementation of a fall protection system becomes essential in safeguarding against accidental falls.

Personal fall protection systems are designed to minimize the risk of injury in the event of a fall by anchoring the individual securely and providing a means of arresting their fall before they can hit the ground. In this scenario, working from a scissor lift suggests a height where the chance of injury from a fall is significant, thereby making the use of fall protection not just a guideline but a crucial safety requirement in compliance with occupational safety regulations.

In contrast, the other tasks listed either involve lower risk situations or do not meet the criteria for requiring a personal fall protection system. For instance, working from a chair that is less than four feet high typically does not present a significant fall risk that necessitates such measures, using a ladder while standing on the top rung is both unsafe and generally against safety protocols, and climbing stairs typically does not require fall protection unless specifically indicated by the environment or height involved.