Retracting life-lines (also called fall-arrest blocks, inertia reels, or fall arrest devices) offer the best protection to a worker in a fall-arrest situation because the webbing or cable retracts to the minimum amount automatically, thereby ensuring the shortest possible fall. If fall clearances are small (see section 13), there may not be enough clearance for a lanyard assembly incorporating a personal energy absorber, as these extend by up to 1.75 metres.
Retracting life-lines are particularly suitable for two situations: repetitive work in a vertical zone, such as up and down a fixed ladder, and on horizontal life-lines (see section 11). Other situations should be treated with caution, because the length of webbing or cable which is sometimes available can allow a major swing fall (see section 14). The shorter retracting life-lines are inherently safer because of this.
Some retracting life-lines may not operate properly outside of a cone of about 30 degrees from the vertical. Also, at greater angles the effect of a swing fall will be greater.
Retracting life-lines will not function correctly if the impact on the line is not sufficient to activate the locking mechanism. This may happen if a worker falls into grain in a grain silo, as the line can continue to fed out without locking because there is no impact on the reel. It can also happen if there is friction of the line running over an edge, or on slopes because a person rolling down an incline may not generate enough inertia to lock the reel. Both these effects apply on roofs, and each alone is a good reason for not using retracting life-lines on a roof.
Generally these devices are designed to be used for falls of up to 600 mm vertically, so the work situation needs to be analysed carefully to ensure that greater falls do not occur. Essentially this means that anchorages must be above head height.