Falling from height is among the most common accident in most construction, shipping and other industries where people have to climb to heights to work or to inspect work.
Most of the time, it ended in death when the falling person hit bottom.
It used to be thought that all that was necessary to save the workers (and, why not, save inspectors too) from this fate was to get them to tie a strong waist belt and tie it to an anchor at the work level, by means of a cable.
Unfortunately, it didn't work out that way. When he (-- although it could be a she, either a worker, or a daring participant in a TV show) fell more than a few metres, after they got him down from his dangling position to the ground (or up to a secure platform), more often than not, they found him dying or dead, generally with no visible injuries.
His insides had been crushed by the shock of the belt when it reached the end of its run. And his spine had been broken.
It was the belt that had killed him. (See graphics below.)

After this bit of wisdom had sunk in, the authorities banned waist belts as a fall arrest device, and recommended the use of a full body harness as shown above.
America banned it in 1998, and other countries (including Singapore) followed soon after.
But then, they found a new set of problems.

The fallen worker, now saved by the harness, still died if he was left dangling for more than anywhere from quarter to three-quarters of an hour, because the heart couldn't keep pumping blood from the feet in that dangling position, with thighs and feet vertical -- it just wasn't designed to do so for longperiods of time.
The dangling man had to be rescued very quickly, so rescue equipment and skills had to be developed -- borrowed from mountain climbing, rappelling, and so on. (See graphics below.)

That wasn't the end of it!
To delay blood clotting and heart attack, they had to train the worker (if he could remain conscious) to stay as upright as possible, and to keep moving his hands and feet, work up his thighs to the horizontal as much as possible.
And finally, when they did get him up (within the brief window of time they had), if he had NOT been upright all this while, they found that when they sat or stood him upright (as most of us would want to do naturally) he died in their arms, because now the heart could not suddenly bear the blood rushing to it from the upper part of the body!
So, they had to make him lie down for a while, until his circulation system settled down to its normal routine, say for quarter of an hour or so.

If you want a more detailed explanation in medical terms, click on the links below:

For information on commercial self-rescue straps, click on link below:

For information on inexpensive substitute rope loops, click on link below: