Under what condition must workers use personal fall arrest systems?

Personal fall arrest systems are crucial for ensuring worker safety when heights pose a risk of falling. The correct condition requiring the use of personal fall arrest systems is when working on structures more than 4 feet above ground. This is aligned with safety regulations and guidelines that specify the necessity of such safety equipment to prevent serious injury or death from falls, which can occur from even a modest height, especially in construction and maintenance environments.

Falling from heights greater than 4 feet significantly increases the risk of injury, making it essential for workers to utilize personal fall arrest systems, which typically include components like harnesses, lifelines, and anchor points. These systems effectively halt a fall, minimizing the potential for injuries associated with free falls.

On the other hand, working on equipment, near large crowds, or on surfaces less than 4 feet above ground does not meet the same criteria for mandatory use of personal fall arrest systems, as the risks associated with those situations are generally lower in terms of fall hazards. Safety regulations focus specifically on heights where falls can lead to severe consequences, making the use of these systems vital in those circumstances.