Abseiling on an artificial tower with a figure 8 device extended with a nylon sling. The sling was threaded directly through the device. I am an instructor and was running a session for children.
When abseiling the equipment appeared set up correctly, so I started my descent, moving quickly so as to help session participants at the bottom of the tower.
After reaching the bottom it became apparent that the abseil rope had been running over the sling, and had melted through over half the width. The sling was since taken out of use.