To ensure an appropriate level of safety when working at height, when placing a personal fall arrest system, the following risk factors should be taken into account and basic rules and recommendations for safe work at height should be followed:
Minimum free space
Safe containment of a falling person must occur in the air (after the phase of the so-called free fall). If a strike occurs against a base or an obstacle, the consequences will always be dangerous to life or health. To prevent such a hazard, a “free space” should be provided in the area below the user. This is a space devoid of barriers that can be hit during a fall. When determining the amount of free space, it is necessary to take into account the parameters of the connecting and shock-absorbing subsystem, as well as the position of the attachment point relative to the user.
Attachment point position
The free fall path should always be as short as possible. The height of the attachment point relative to the position of the user of the system determines the length of the free fall path. If the point of attachment of the connecting and shock-absorbing subsystem is above the worker, the fall path will be shortened as much as possible. On the other hand, positioning the anchor point below the worker's position will increase the fall path, which may lead to impact on the surface below, or cause a threat of excessive impact force accompanying the fall containment. In a situation where there is an alternative, the user should choose an anchor point located as high as possible.
This is a dangerous phenomenon based on the pendulum nature of free fall, during which there is a risk of hitting obstacles located on the side. Removing the user from the vertical, which is defined by a line drawn from the anchor point, increases the possibility of a pendulum effect. If the angle of deviation from the vertical is less than 30 degrees, the threat of the pendulum effect is low, if more - high. Therefore, when choosing an attachment point, one should strive to reduce the threat associated with the pendulum effect.