What is fall factor?

What is fall factor? And why is it important?

When working at height, the position of the user’s attachment point to the personal fall protection system relative to the anchor point is important to consider; this determines the “fall factor”, which provides an indication of the length and severity of a potential fall.

Fall factor is calculated by taking the free fall distance and dividing it by the length of lanyard available to arrest it. In a normal work situation, the maximum fall factor is 2.

The fall factor should always be kept as small as possible, i.e. the length of any potential fall should be minimised, for example by choosing an anchor point above the user, and the length of the lanyard should be kept as short as possible.

As illustrated below, an anchor point above the user gives the smallest fall factor, so is the safest, and is the preferred option; an anchor point at shoulder level gives a larger fall factor and should only be used as a second choice; an anchor point at foot level gives the maximum fall factor and whilst acceptable should always be the last option.

For a 2-metre lanyard:

A. Anchor point above user (preferred option).

Free fall distance: 0.5 m (F)

Fall factor = 0.5/2 =0.25

B. Anchor point at shoulder level (non-preferred option).

Free fall distance: 2m (F)

Fall factor = 2/2 =1

C. Anchor point at foot level (only if there is no other option).

Free fall distance: 4m (F)

Fall factor = 4/2 =2

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