You’ve heard it over and over again… ” If you are more than six feet off the ground you need to be tied off”.
Understanding the fall distance calculation, however, is important to the “how” of being tied off.
It’s simply an issue of addition. Let’s look at the different part that we need to add up:
- Lanyard Length: six (6) feet total
- Deceleration Distance: Three and a half (3.5) feet
- Distance from the sole of the feet to the top of the back D-ring once the fall has occurred: Six (6) feet
- Safety Factor: three (3) feet
Now, let’s add these up: 6 + 3.5 + 6 + 3 = 18.5 feet
What this means is that if you take a fall when you anchor point is lower than 18 ½ feet above the ground (or the floor, at whatever level you are at) then you stand a very good chance of getting seriously injured or even killed.
Guardian Fall Protection provides us with this illustration:
(You can download a PDF of this from their website here).
So next time you’re looking for an anchor point, just remember that it needs to be at least 18.5 feet above the surface you are trying to keep from impacting.